From bb3226a54ba0eb9d261589e989f0c1e422bf65dc Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Sun, 28 Sep 2025 15:51:54 +0200
Subject: [PATCH 01/25] Backport `Objects.checkFromIndexSize` to `IOUtils`

Java 9 introduced `Objects.checkFromIndexSize` for validating the offset/length ranges used in `read` and `write` operations.

This PR adds an equivalent method, `IOUtils.checkFromIndexSize`, to provide the same validation in Commons IO. It simplifies range checks in stream implementations and makes the utility available to projects that still target Java 8.
---
 .../java/org/apache/commons/io/IOUtils.java   | 30 +++++++++++
 .../org/apache/commons/io/IOUtilsTest.java    | 52 +++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index e37eddafb3f..eb611f80584 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -406,6 +406,36 @@ private static char[] charArray(final int size) {
         return new char[size];
     }
 
+    /**
+     * Checks if the sub-range described by an offset and length is valid for an array of the given length.
+     *
+     * <p>This method is functionally equivalent to
+     * {@code java.util.Objects#checkFromIndexSize(int, int, int)} introduced in Java 9,
+     * but is provided here for use on Java 8.</p>
+     *
+     * <p>The range is valid if all of the following hold:</p>
+     * <ul>
+     *   <li>{@code off >= 0}</li>
+     *   <li>{@code len >= 0}</li>
+     *   <li>{@code arrayLength >= 0}</li>
+     *   <li>{@code off + len <= arrayLength}</li>
+     * </ul>
+     *
+     * <p>If the range is invalid, this method throws an
+     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     *
+     * @param off         the starting offset into the array
+     * @param len         the number of elements in the range
+     * @param arrayLength the length of the array to be checked against
+     * @throws IndexOutOfBoundsException if the range {@code [off, off + len)} is out of bounds
+     * @since 2.21.0
+     */
+    public static void checkFromIndexSize(final int off, final int len, final int arrayLength) {
+        if ((off | len | arrayLength) < 0 || arrayLength - len < off) {
+            throw new IndexOutOfBoundsException(String.format("Range [%s, %<s + %s) out of bounds for length %s", off, len, arrayLength));
+        }
+    }
+
     /**
      * Clears any state.
      * <ul>
diff --git a/src/test/java/org/apache/commons/io/IOUtilsTest.java b/src/test/java/org/apache/commons/io/IOUtilsTest.java
index bae8f59e374..d062ae61ea8 100644
--- a/src/test/java/org/apache/commons/io/IOUtilsTest.java
+++ b/src/test/java/org/apache/commons/io/IOUtilsTest.java
@@ -50,6 +50,7 @@
 import java.io.SequenceInputStream;
 import java.io.StringReader;
 import java.io.Writer;
+import java.lang.reflect.InvocationTargetException;
 import java.net.ServerSocket;
 import java.net.Socket;
 import java.net.URI;
@@ -65,6 +66,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -85,7 +87,9 @@
 import org.apache.commons.io.output.UnsynchronizedByteArrayOutputStream;
 import org.apache.commons.io.test.TestUtils;
 import org.apache.commons.io.test.ThrowOnCloseReader;
+import org.apache.commons.lang3.JavaVersion;
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.SystemUtils;
 import org.apache.commons.lang3.exception.ExceptionUtils;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
@@ -348,6 +352,54 @@ void testByteArrayWithNegativeSize() {
         assertThrows(NegativeArraySizeException.class, () -> IOUtils.byteArray(-1));
     }
 
+    static Stream<Arguments> testCheckFromIndexSizeValidCases() {
+        return Stream.of(
+                // Valid cases
+                Arguments.of(0, 0, 42),
+                Arguments.of(0, 1, 42),
+                Arguments.of(0, 42, 42),
+                Arguments.of(41, 1, 42),
+                Arguments.of(42, 0, 42)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void testCheckFromIndexSizeValidCases(int off, int len, int arrayLength) {
+        assertDoesNotThrow(() -> IOUtils.checkFromIndexSize(off, len, arrayLength));
+    }
+
+    static Stream<Arguments> testCheckFromIndexSizeInvalidCases() {
+        return Stream.of(
+                Arguments.of(-1, 0, 42),
+                Arguments.of(0, -1, 42),
+                Arguments.of(0, 0, -1),
+                // off + len > arrayLength
+                Arguments.of(1, 42, 42),
+                Arguments.of(Integer.MAX_VALUE, 1, Integer.MAX_VALUE)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void testCheckFromIndexSizeInvalidCases(int off, int len, int arrayLength) {
+        final IndexOutOfBoundsException ex = assertThrows(IndexOutOfBoundsException.class, () -> IOUtils.checkFromIndexSize(off, len, arrayLength));
+        assertTrue(ex.getMessage().contains(String.valueOf(off)));
+        assertTrue(ex.getMessage().contains(String.valueOf(len)));
+        assertTrue(ex.getMessage().contains(String.valueOf(arrayLength)));
+        // Optional requirement: compare the exception message for Java 8 and Java 9+
+        if (SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_9)) {
+            final IndexOutOfBoundsException jreEx = assertThrows(IndexOutOfBoundsException.class, () -> {
+                try {
+                    Objects.class.getDeclaredMethod("checkFromIndexSize", int.class, int.class, int.class).invoke(null, off, len, arrayLength);
+                } catch (InvocationTargetException ite) {
+                    throw ite.getTargetException();
+                }
+            });
+            assertEquals(jreEx.getMessage(), ex.getMessage());
+        }
+    }
+
     @Test
     void testClose() {
         assertDoesNotThrow(() -> IOUtils.close((Closeable) null));

From 659b90bdccb1e5a14ad59c87ab9141b7a70f894e Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Sun, 28 Sep 2025 15:56:19 +0200
Subject: [PATCH 02/25] Add changelog entry

---
 src/changes/changes.xml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 0190734a841..7c2b0971b29 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -68,6 +68,7 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add"                due-to="Gary Gregory">Add IOIterable.asIterable().</action>
       <action dev="pkarwasz" type="add"                due-to="Piotr P. Karwasz">Add NIO channel support to `AbstractStreamBuilder`.</action>
       <action dev="pkarwasz" type="add"                due-to="Piotr P. Karwasz">Add CloseShieldChannel to close-shielded NIO Channels #786.</action>
+      <action dev="pkarwasz" type="add"                due-to="Piotr P. Karwasz">Added IOUtils.checkFromIndexSize as a Java 8 backport of Objects.checkFromIndexSize #790.</action>
       <!-- UPDATE -->
       <action type="update" dev="ggregory"             due-to="Gary Gregory, Dependabot">Bump org.apache.commons:commons-parent from 85 to 88 #774, #783.</action>
       <action type="update" dev="ggregory"             due-to="Gary Gregory">[test] Bump commons-codec:commons-codec from 1.18.0 to 1.19.0.</action>

From 5552d9b1495b9315210e3b7ab9320bc92f89cb5c Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Sun, 28 Sep 2025 20:37:14 +0200
Subject: [PATCH 03/25] fix: apply `IOUtils.checkIndexFromSize` to all streams

---
 .../java/org/apache/commons/io/IOUtils.java   | 125 ++++++++++++++----
 .../commons/io/input/BOMInputStream.java      |   4 +
 .../commons/io/input/BoundedReader.java       |   3 +
 .../apache/commons/io/input/BrokenReader.java |   5 +
 .../input/BufferedFileChannelInputStream.java |   5 +-
 .../io/input/CharSequenceInputStream.java     |   6 +-
 .../commons/io/input/CharSequenceReader.java  |  12 +-
 .../commons/io/input/ClosedInputStream.java   |   4 +
 .../apache/commons/io/input/ClosedReader.java |   4 +
 .../io/input/MemoryMappedFileInputStream.java |   5 +
 .../commons/io/input/NullInputStream.java     |   5 +-
 .../apache/commons/io/input/NullReader.java   |   6 +
 .../commons/io/input/QueueInputStream.java    |   9 +-
 .../io/input/ReadAheadInputStream.java        |   5 +-
 .../commons/io/input/ReaderInputStream.java   |   8 +-
 .../commons/io/input/SequenceReader.java      |   7 +-
 .../UnsynchronizedBufferedInputStream.java    |  11 +-
 .../input/UnsynchronizedBufferedReader.java   |   8 +-
 .../UnsynchronizedByteArrayInputStream.java   |   7 +-
 .../buffer/CircularBufferInputStream.java     |   9 +-
 .../commons/io/output/AppendableWriter.java   |   7 +-
 .../commons/io/output/BrokenWriter.java       |   2 +
 .../io/output/ByteArrayOutputStream.java      |  10 +-
 .../io/output/ChunkedOutputStream.java        |   1 +
 .../commons/io/output/ChunkedWriter.java      |   1 +
 .../commons/io/output/ClosedOutputStream.java |   3 +
 .../commons/io/output/ClosedWriter.java       |   3 +
 .../io/output/FilterCollectionWriter.java     |   3 +
 .../commons/io/output/NullAppendable.java     |   3 +
 .../commons/io/output/NullOutputStream.java   |   4 +-
 .../apache/commons/io/output/NullWriter.java  |   6 +-
 .../io/output/StringBuilderWriter.java        |   7 +-
 .../io/output/ThresholdingOutputStream.java   |   2 +
 .../UnsynchronizedByteArrayOutputStream.java  |   5 +-
 .../commons/io/output/WriterOutputStream.java |   1 +
 .../commons/io/output/XmlStreamWriter.java    |   1 +
 .../org/apache/commons/io/IOUtilsTest.java    |  50 +++++++
 37 files changed, 262 insertions(+), 95 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index eb611f80584..0d671eac9ee 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -17,6 +17,8 @@
 
 package org.apache.commons.io;
 
+import static java.util.Objects.requireNonNull;
+
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
@@ -244,7 +246,7 @@ public class IOUtils {
     public static BufferedInputStream buffer(final InputStream inputStream) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        Objects.requireNonNull(inputStream, "inputStream");
+        requireNonNull(inputStream, "inputStream");
         return inputStream instanceof BufferedInputStream ?
                 (BufferedInputStream) inputStream : new BufferedInputStream(inputStream);
     }
@@ -263,7 +265,7 @@ public static BufferedInputStream buffer(final InputStream inputStream) {
     public static BufferedInputStream buffer(final InputStream inputStream, final int size) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        Objects.requireNonNull(inputStream, "inputStream");
+        requireNonNull(inputStream, "inputStream");
         return inputStream instanceof BufferedInputStream ?
                 (BufferedInputStream) inputStream : new BufferedInputStream(inputStream, size);
     }
@@ -281,7 +283,7 @@ public static BufferedInputStream buffer(final InputStream inputStream, final in
     public static BufferedOutputStream buffer(final OutputStream outputStream) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        Objects.requireNonNull(outputStream, "outputStream");
+        requireNonNull(outputStream, "outputStream");
         return outputStream instanceof BufferedOutputStream ?
                 (BufferedOutputStream) outputStream : new BufferedOutputStream(outputStream);
     }
@@ -300,7 +302,7 @@ public static BufferedOutputStream buffer(final OutputStream outputStream) {
     public static BufferedOutputStream buffer(final OutputStream outputStream, final int size) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        Objects.requireNonNull(outputStream, "outputStream");
+        requireNonNull(outputStream, "outputStream");
         return outputStream instanceof BufferedOutputStream ?
                 (BufferedOutputStream) outputStream : new BufferedOutputStream(outputStream, size);
     }
@@ -407,35 +409,112 @@ private static char[] charArray(final int size) {
     }
 
     /**
-     * Checks if the sub-range described by an offset and length is valid for an array of the given length.
+     * Checks if the sub-range described by an offset and length is valid for the given array.
+     *
+     * <p>The range is valid if all of the following hold:</p>
+     * <ul>
+     *   <li>{@code off >= 0}</li>
+     *   <li>{@code len >= 0}</li>
+     *   <li>{@code off + len <= array.length}</li>
+     * </ul>
+     *
+     * <p>If the range is invalid, this method throws an
+     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     *
+     * @param array       The array to be checked against
+     * @param off         The starting offset into the array
+     * @param len         The number of elements in the range
+     * @throws NullPointerException      If the array is null
+     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
+     * @since 2.21.0
+     */
+    public static void checkFromIndexSize(final byte[] array, final int off, final int len) {
+        checkFromIndexSize(off, len, requireNonNull(array, "byte array").length);
+    }
+
+    /**
+     * Checks if the sub-range described by an offset and length is valid for the given array.
+     *
+     * <p>The range is valid if all of the following hold:</p>
+     * <ul>
+     *   <li>{@code off >= 0}</li>
+     *   <li>{@code len >= 0}</li>
+     *   <li>{@code off + len <= array.length}</li>
+     * </ul>
+     *
+     * <p>If the range is invalid, this method throws an
+     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
      *
-     * <p>This method is functionally equivalent to
-     * {@code java.util.Objects#checkFromIndexSize(int, int, int)} introduced in Java 9,
-     * but is provided here for use on Java 8.</p>
+     * @param array       The array to be checked against
+     * @param off         The starting offset into the array
+     * @param len         The number of elements in the range
+     * @throws NullPointerException      If the array is null
+     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
+     * @since 2.21.0
+     */
+    public static void checkFromIndexSize(final char[] array, final int off, final int len) {
+        checkFromIndexSize(off, len, requireNonNull(array, "char array").length);
+    }
+
+    /**
+     * Checks if the sub-range described by an offset and length is valid for the given string.
      *
      * <p>The range is valid if all of the following hold:</p>
      * <ul>
      *   <li>{@code off >= 0}</li>
      *   <li>{@code len >= 0}</li>
-     *   <li>{@code arrayLength >= 0}</li>
-     *   <li>{@code off + len <= arrayLength}</li>
+     *   <li>{@code off + len <= array.length}</li>
      * </ul>
      *
      * <p>If the range is invalid, this method throws an
      * {@link IndexOutOfBoundsException} with a descriptive message.</p>
      *
-     * @param off         the starting offset into the array
-     * @param len         the number of elements in the range
-     * @param arrayLength the length of the array to be checked against
-     * @throws IndexOutOfBoundsException if the range {@code [off, off + len)} is out of bounds
+     * @param str         The char sequence to be checked against
+     * @param off         The starting offset into the array
+     * @param len         The number of elements in the range
+     * @throws NullPointerException      If the array is null
+     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
      * @since 2.21.0
      */
-    public static void checkFromIndexSize(final int off, final int len, final int arrayLength) {
+    public static void checkFromIndexSize(final String str, final int off, final int len) {
+        checkFromIndexSize(off, len, requireNonNull(str, "str").length());
+    }
+
+    static void checkFromIndexSize(final int off, final int len, final int arrayLength) {
         if ((off | len | arrayLength) < 0 || arrayLength - len < off) {
             throw new IndexOutOfBoundsException(String.format("Range [%s, %<s + %s) out of bounds for length %s", off, len, arrayLength));
         }
     }
 
+    /**
+     * Checks if the sub-sequence described by fromIndex (inclusive) and toIndex (exclusive) is valid for the given {@link CharSequence}.
+     *
+     * <p>The range is valid if all of the following hold:</p>
+     * <ul>
+     *     <li>{@code fromIndex >= 0}</li>
+     *     <li>{@code fromIndex <= toIndex}</li>
+     *     <li>{@code toIndex <= seq.length()}</li>
+     * </ul>
+     *
+     * <p>If the range is invalid, this method throws an {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     *
+     * @param seq The char sequence to be checked against
+     * @param fromIndex The starting index into the char sequence (inclusive)
+     * @param toIndex The ending index into the char sequence (exclusive)
+     * @throws NullPointerException If the char sequence is null
+     * @throws IndexOutOfBoundsException If the range {@code [fromIndex, toIndex)} is out of bounds
+     * @since 2.21.0
+     */
+    public static void checkFromToIndex(final CharSequence seq, int fromIndex, final int toIndex) {
+        checkFromToIndex(fromIndex, toIndex, requireNonNull(seq, "char sequence").length());
+    }
+
+    static void checkFromToIndex(final int fromIndex, final int toIndex, final int length) {
+        if (fromIndex < 0 | toIndex < fromIndex | length < toIndex) {
+            throw new IndexOutOfBoundsException(String.format("Range [%s, %s) out of bounds for length %s", fromIndex, toIndex, length));
+        }
+    }
+
     /**
      * Clears any state.
      * <ul>
@@ -1217,7 +1296,7 @@ public static void copy(final InputStream input, final Writer writer, final Stri
      */
     @SuppressWarnings("resource") // streams are closed by the caller.
     public static QueueInputStream copy(final java.io.ByteArrayOutputStream outputStream) throws IOException {
-        Objects.requireNonNull(outputStream, "outputStream");
+        requireNonNull(outputStream, "outputStream");
         final QueueInputStream in = new QueueInputStream();
         outputStream.writeTo(in.newQueueOutputStream());
         return in;
@@ -1398,7 +1477,7 @@ public static int copy(final Reader reader, final Writer writer) throws IOExcept
      * @since 2.9.0
      */
     public static long copy(final URL url, final File file) throws IOException {
-        try (OutputStream outputStream = Files.newOutputStream(Objects.requireNonNull(file, "file").toPath())) {
+        try (OutputStream outputStream = Files.newOutputStream(requireNonNull(file, "file").toPath())) {
             return copy(url, outputStream);
         }
     }
@@ -1421,7 +1500,7 @@ public static long copy(final URL url, final File file) throws IOException {
      * @since 2.9.0
      */
     public static long copy(final URL url, final OutputStream outputStream) throws IOException {
-        try (InputStream inputStream = Objects.requireNonNull(url, "url").openStream()) {
+        try (InputStream inputStream = requireNonNull(url, "url").openStream()) {
             return copyLarge(inputStream, outputStream);
         }
     }
@@ -1470,8 +1549,8 @@ public static long copyLarge(final InputStream inputStream, final OutputStream o
     @SuppressWarnings("resource") // streams are closed by the caller.
     public static long copyLarge(final InputStream inputStream, final OutputStream outputStream, final byte[] buffer)
         throws IOException {
-        Objects.requireNonNull(inputStream, "inputStream");
-        Objects.requireNonNull(outputStream, "outputStream");
+        requireNonNull(inputStream, "inputStream");
+        requireNonNull(outputStream, "outputStream");
         long count = 0;
         int n;
         while (EOF != (n = inputStream.read(buffer))) {
@@ -2739,7 +2818,7 @@ public static byte[] toByteArray(final InputStream inputStream) throws IOExcepti
      * @since 2.1
      */
     public static byte[] toByteArray(final InputStream input, final int size) throws IOException {
-        return toByteArray(Objects.requireNonNull(input, "input")::read, size);
+        return toByteArray(requireNonNull(input, "input")::read, size);
     }
 
     /**
@@ -2765,7 +2844,7 @@ public static byte[] toByteArray(final InputStream input, final int size) throws
      * @since 2.21.0
      */
     public static byte[] toByteArray(final InputStream input, final int size, final int chunkSize) throws IOException {
-        Objects.requireNonNull(input, "input");
+        requireNonNull(input, "input");
         if (chunkSize <= 0) {
             throw new IllegalArgumentException("Chunk size must be greater than zero: " + chunkSize);
         }
@@ -3913,7 +3992,7 @@ public static void writeLines(final Collection<?> lines, String lineEnding, fina
      * @since 2.7
      */
     public static Writer writer(final Appendable appendable) {
-        Objects.requireNonNull(appendable, "appendable");
+        requireNonNull(appendable, "appendable");
         if (appendable instanceof Writer) {
             return (Writer) appendable;
         }
diff --git a/src/main/java/org/apache/commons/io/input/BOMInputStream.java b/src/main/java/org/apache/commons/io/input/BOMInputStream.java
index c5872d7cbc9..4cb347f1dc5 100644
--- a/src/main/java/org/apache/commons/io/input/BOMInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/BOMInputStream.java
@@ -444,6 +444,10 @@ public int read(final byte[] buf) throws IOException {
      */
     @Override
     public int read(final byte[] buf, int off, int len) throws IOException {
+        IOUtils.checkFromIndexSize(buf, off, len);
+        if (len == 0) {
+            return 0;
+        }
         int firstCount = 0;
         int b = 0;
         while (len > 0 && b >= 0) {
diff --git a/src/main/java/org/apache/commons/io/input/BoundedReader.java b/src/main/java/org/apache/commons/io/input/BoundedReader.java
index 3cd0cee6259..c64759045f2 100644
--- a/src/main/java/org/apache/commons/io/input/BoundedReader.java
+++ b/src/main/java/org/apache/commons/io/input/BoundedReader.java
@@ -23,6 +23,8 @@
 import java.io.IOException;
 import java.io.Reader;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * A reader that imposes a limit to the number of characters that can be read from an underlying reader, returning EOF
  * when this limit is reached, regardless of state of underlying reader.
@@ -121,6 +123,7 @@ public int read() throws IOException {
      */
     @Override
     public int read(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         int c;
         for (int i = 0; i < len; i++) {
             c = read();
diff --git a/src/main/java/org/apache/commons/io/input/BrokenReader.java b/src/main/java/org/apache/commons/io/input/BrokenReader.java
index 8fb510569cf..61e9bff47ba 100644
--- a/src/main/java/org/apache/commons/io/input/BrokenReader.java
+++ b/src/main/java/org/apache/commons/io/input/BrokenReader.java
@@ -20,6 +20,7 @@
 import java.io.Reader;
 import java.util.function.Supplier;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.Erase;
 
 /**
@@ -114,6 +115,10 @@ public void mark(final int readAheadLimit) throws IOException {
      */
     @Override
     public int read(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
+        if (len == 0) {
+            return 0;
+        }
         throw rethrow();
     }
 
diff --git a/src/main/java/org/apache/commons/io/input/BufferedFileChannelInputStream.java b/src/main/java/org/apache/commons/io/input/BufferedFileChannelInputStream.java
index bc5a9533038..8e81b34508a 100644
--- a/src/main/java/org/apache/commons/io/input/BufferedFileChannelInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/BufferedFileChannelInputStream.java
@@ -254,8 +254,9 @@ public synchronized int read() throws IOException {
 
     @Override
     public synchronized int read(final byte[] b, final int offset, int len) throws IOException {
-        if (offset < 0 || len < 0 || offset + len < 0 || offset + len > b.length) {
-            throw new IndexOutOfBoundsException();
+        IOUtils.checkFromIndexSize(b, offset, len);
+        if (len == 0) {
+            return 0;
         }
         if (!refill()) {
             return EOF;
diff --git a/src/main/java/org/apache/commons/io/input/CharSequenceInputStream.java b/src/main/java/org/apache/commons/io/input/CharSequenceInputStream.java
index 8666105491a..874dcf1cb39 100644
--- a/src/main/java/org/apache/commons/io/input/CharSequenceInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/CharSequenceInputStream.java
@@ -28,7 +28,6 @@
 import java.nio.charset.CharsetEncoder;
 import java.nio.charset.CoderResult;
 import java.nio.charset.CodingErrorAction;
-import java.util.Objects;
 
 import org.apache.commons.io.Charsets;
 import org.apache.commons.io.IOUtils;
@@ -319,10 +318,7 @@ public int read(final byte[] b) throws IOException {
 
     @Override
     public int read(final byte[] array, int off, int len) throws IOException {
-        Objects.requireNonNull(array, "array");
-        if (len < 0 || off + len > array.length) {
-            throw new IndexOutOfBoundsException("Array Size=" + array.length + ", offset=" + off + ", length=" + len);
-        }
+        IOUtils.checkFromIndexSize(array, off, len);
         if (len == 0) {
             return 0; // must return 0 for zero length read
         }
diff --git a/src/main/java/org/apache/commons/io/input/CharSequenceReader.java b/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
index 8fee366b2da..bc3defe7ddc 100644
--- a/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
+++ b/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
@@ -20,7 +20,8 @@
 
 import java.io.Reader;
 import java.io.Serializable;
-import java.util.Objects;
+
+import org.apache.commons.io.IOUtils;
 
 /**
  * {@link Reader} implementation that can read from String, StringBuffer,
@@ -209,14 +210,13 @@ public int read() {
      */
     @Override
     public int read(final char[] array, final int offset, final int length) {
+        IOUtils.checkFromIndexSize(array, offset, length);
+        if (length == 0) {
+            return 0;
+        }
         if (idx >= end()) {
             return EOF;
         }
-        Objects.requireNonNull(array, "array");
-        if (length < 0 || offset < 0 || offset + length > array.length) {
-            throw new IndexOutOfBoundsException("Array Size=" + array.length +
-                    ", offset=" + offset + ", length=" + length);
-        }
 
         if (charSequence instanceof String) {
             final int count = Math.min(length, end() - idx);
diff --git a/src/main/java/org/apache/commons/io/input/ClosedInputStream.java b/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
index ceab0176090..5ddb9ea6c9d 100644
--- a/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
@@ -86,6 +86,10 @@ public int read() {
      */
     @Override
     public int read(final byte[] b, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(b, off, len);
+        if (len == 0) {
+            return 0;
+        }
         return EOF;
     }
 
diff --git a/src/main/java/org/apache/commons/io/input/ClosedReader.java b/src/main/java/org/apache/commons/io/input/ClosedReader.java
index 93c99e3c550..72220c6978d 100644
--- a/src/main/java/org/apache/commons/io/input/ClosedReader.java
+++ b/src/main/java/org/apache/commons/io/input/ClosedReader.java
@@ -71,6 +71,10 @@ public void close() throws IOException {
      */
     @Override
     public int read(final char[] cbuf, final int off, final int len) {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
+        if (len == 0) {
+            return 0;
+        }
         return EOF;
     }
 
diff --git a/src/main/java/org/apache/commons/io/input/MemoryMappedFileInputStream.java b/src/main/java/org/apache/commons/io/input/MemoryMappedFileInputStream.java
index 8fdd7aec8b9..22fae70ca75 100644
--- a/src/main/java/org/apache/commons/io/input/MemoryMappedFileInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/MemoryMappedFileInputStream.java
@@ -27,6 +27,7 @@
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.build.AbstractStreamBuilder;
 
 /**
@@ -216,6 +217,10 @@ public int read() throws IOException {
 
     @Override
     public int read(final byte[] b, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(b, off, len);
+        if (len == 0) {
+            return 0;
+        }
         checkOpen();
         if (!buffer.hasRemaining()) {
             nextBuffer();
diff --git a/src/main/java/org/apache/commons/io/input/NullInputStream.java b/src/main/java/org/apache/commons/io/input/NullInputStream.java
index 5f3497863b0..32b1206ff2f 100644
--- a/src/main/java/org/apache/commons/io/input/NullInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/NullInputStream.java
@@ -22,6 +22,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * A lightweight {@link InputStream} that emulates a stream of a specified size.
  * <p>
@@ -292,7 +294,8 @@ public int read(final byte[] bytes) throws IOException {
      */
     @Override
     public int read(final byte[] bytes, final int offset, final int length) throws IOException {
-        if (bytes.length == 0 || length == 0) {
+        IOUtils.checkFromIndexSize(bytes, offset, length);
+        if (length == 0) {
             return 0;
         }
         checkOpen();
diff --git a/src/main/java/org/apache/commons/io/input/NullReader.java b/src/main/java/org/apache/commons/io/input/NullReader.java
index c5ae530a170..2b7fdb47175 100644
--- a/src/main/java/org/apache/commons/io/input/NullReader.java
+++ b/src/main/java/org/apache/commons/io/input/NullReader.java
@@ -22,6 +22,8 @@
 import java.io.IOException;
 import java.io.Reader;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * A functional, lightweight {@link Reader} that emulates
  * a reader of a specified size.
@@ -276,6 +278,10 @@ public int read(final char[] chars) throws IOException {
      */
     @Override
     public int read(final char[] chars, final int offset, final int length) throws IOException {
+        IOUtils.checkFromIndexSize(chars, offset, length);
+        if (length == 0) {
+            return 0;
+        }
         if (eof) {
             throw new IOException("Read after end of file");
         }
diff --git a/src/main/java/org/apache/commons/io/input/QueueInputStream.java b/src/main/java/org/apache/commons/io/input/QueueInputStream.java
index 1515eb94036..5f701945cb3 100644
--- a/src/main/java/org/apache/commons/io/input/QueueInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/QueueInputStream.java
@@ -30,6 +30,7 @@
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.build.AbstractStreamBuilder;
 import org.apache.commons.io.output.QueueOutputStream;
 
@@ -244,13 +245,7 @@ public int read() {
      */
     @Override
     public int read(final byte[] b, final int offset, final int length) {
-        if (b == null) {
-            throw new NullPointerException();
-        }
-        if (offset < 0 || length < 0 || length > b.length - offset) {
-            throw new IndexOutOfBoundsException(
-                    String.format("Range [%d, %<d + %d) out of bounds for length %d", offset, length, b.length));
-        }
+        IOUtils.checkFromIndexSize(b, offset, length);
         if (length == 0) {
             return 0;
         }
diff --git a/src/main/java/org/apache/commons/io/input/ReadAheadInputStream.java b/src/main/java/org/apache/commons/io/input/ReadAheadInputStream.java
index 08e0182373e..bcee009a431 100644
--- a/src/main/java/org/apache/commons/io/input/ReadAheadInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/ReadAheadInputStream.java
@@ -30,6 +30,7 @@
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.ReentrantLock;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.build.AbstractStreamBuilder;
 
 /**
@@ -341,9 +342,7 @@ public int read() throws IOException {
 
     @Override
     public int read(final byte[] b, final int offset, int len) throws IOException {
-        if (offset < 0 || len < 0 || len > b.length - offset) {
-            throw new IndexOutOfBoundsException();
-        }
+        IOUtils.checkFromIndexSize(b, offset, len);
         if (len == 0) {
             return 0;
         }
diff --git a/src/main/java/org/apache/commons/io/input/ReaderInputStream.java b/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
index bcd03abd565..b2b6a82befb 100644
--- a/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
@@ -30,7 +30,6 @@
 import java.nio.charset.CharsetEncoder;
 import java.nio.charset.CoderResult;
 import java.nio.charset.CodingErrorAction;
-import java.util.Objects;
 
 import org.apache.commons.io.Charsets;
 import org.apache.commons.io.IOUtils;
@@ -456,14 +455,11 @@ public int read(final byte[] b) throws IOException {
      */
     @Override
     public int read(final byte[] array, int off, int len) throws IOException {
-        Objects.requireNonNull(array, "array");
-        if (len < 0 || off < 0 || off + len > array.length) {
-            throw new IndexOutOfBoundsException("Array size=" + array.length + ", offset=" + off + ", length=" + len);
-        }
-        int read = 0;
+        IOUtils.checkFromIndexSize(array, off, len);
         if (len == 0) {
             return 0; // Always return 0 if len == 0
         }
+        int read = 0;
         while (len > 0) {
             if (encoderOut.hasRemaining()) { // Data from the last read not fully copied
                 final int c = Math.min(encoderOut.remaining(), len);
diff --git a/src/main/java/org/apache/commons/io/input/SequenceReader.java b/src/main/java/org/apache/commons/io/input/SequenceReader.java
index 6632917030b..b10bfcefcc9 100644
--- a/src/main/java/org/apache/commons/io/input/SequenceReader.java
+++ b/src/main/java/org/apache/commons/io/input/SequenceReader.java
@@ -25,6 +25,7 @@
 import java.util.Iterator;
 import java.util.Objects;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.Uncheck;
 
 /**
@@ -114,9 +115,9 @@ public int read() throws IOException {
      */
     @Override
     public int read(final char[] cbuf, int off, int len) throws IOException {
-        Objects.requireNonNull(cbuf, "cbuf");
-        if (len < 0 || off < 0 || off + len > cbuf.length) {
-            throw new IndexOutOfBoundsException("Array Size=" + cbuf.length + ", offset=" + off + ", length=" + len);
+        IOUtils.checkFromIndexSize(cbuf, off, len);
+        if (len == 0) {
+            return 0;
         }
         int count = 0;
         while (reader != null) {
diff --git a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedInputStream.java b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedInputStream.java
index 8106a065631..8d60f6cedb8 100644
--- a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedInputStream.java
@@ -306,19 +306,16 @@ public int read() throws IOException {
      */
     @Override
     public int read(final byte[] dest, int offset, final int length) throws IOException {
+        IOUtils.checkFromIndexSize(dest, offset, length);
+        if (length == 0) {
+            return 0;
+        }
         // Use local ref since buf may be invalidated by an unsynchronized
         // close()
         byte[] localBuf = buffer;
         if (localBuf == null) {
             throw new IOException("Stream is closed");
         }
-        // avoid int overflow
-        if (offset > dest.length - length || offset < 0 || length < 0) {
-            throw new IndexOutOfBoundsException();
-        }
-        if (length == 0) {
-            return 0;
-        }
         final InputStream localIn = inputStream;
         if (localIn == null) {
             throw new IOException("Stream is closed");
diff --git a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
index 51b48c07af3..e8bf3363f05 100644
--- a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
+++ b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
@@ -271,10 +271,12 @@ public int read() throws IOException {
      */
     @Override
     public int read(final char[] buffer, int offset, final int length) throws IOException {
-        checkOpen();
-        if (offset < 0 || offset > buffer.length - length || length < 0) {
-            throw new IndexOutOfBoundsException();
+        IOUtils.checkFromIndexSize(buffer, offset, length);
+        if (length == 0) {
+            return 0;
         }
+        checkOpen();
+
         int outstanding = length;
         while (outstanding > 0) {
 
diff --git a/src/main/java/org/apache/commons/io/input/UnsynchronizedByteArrayInputStream.java b/src/main/java/org/apache/commons/io/input/UnsynchronizedByteArrayInputStream.java
index cb2f5d3ddc5..a56dec7206c 100644
--- a/src/main/java/org/apache/commons/io/input/UnsynchronizedByteArrayInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/UnsynchronizedByteArrayInputStream.java
@@ -21,6 +21,7 @@
 import java.io.InputStream;
 import java.util.Objects;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.build.AbstractOrigin;
 import org.apache.commons.io.build.AbstractStreamBuilder;
 
@@ -288,9 +289,9 @@ public int read(final byte[] dest) {
 
     @Override
     public int read(final byte[] dest, final int off, final int len) {
-        Objects.requireNonNull(dest, "dest");
-        if (off < 0 || len < 0 || off + len > dest.length) {
-            throw new IndexOutOfBoundsException();
+        IOUtils.checkFromIndexSize(dest, off, len);
+        if (len == 0) {
+            return 0;
         }
 
         if (offset >= eod) {
diff --git a/src/main/java/org/apache/commons/io/input/buffer/CircularBufferInputStream.java b/src/main/java/org/apache/commons/io/input/buffer/CircularBufferInputStream.java
index 8be305ddd04..b92163478d0 100644
--- a/src/main/java/org/apache/commons/io/input/buffer/CircularBufferInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/buffer/CircularBufferInputStream.java
@@ -125,12 +125,9 @@ public int read() throws IOException {
 
     @Override
     public int read(final byte[] targetBuffer, final int offset, final int length) throws IOException {
-        Objects.requireNonNull(targetBuffer, "targetBuffer");
-        if (offset < 0) {
-            throw new IllegalArgumentException("Offset must not be negative");
-        }
-        if (length < 0) {
-            throw new IllegalArgumentException("Length must not be negative");
+        IOUtils.checkFromIndexSize(targetBuffer, offset, length);
+        if (length == 0) {
+            return 0;
         }
         if (!haveBytes(length)) {
             return EOF;
diff --git a/src/main/java/org/apache/commons/io/output/AppendableWriter.java b/src/main/java/org/apache/commons/io/output/AppendableWriter.java
index 2130e448dea..a6f4ff53fa9 100644
--- a/src/main/java/org/apache/commons/io/output/AppendableWriter.java
+++ b/src/main/java/org/apache/commons/io/output/AppendableWriter.java
@@ -21,6 +21,8 @@
 import java.io.Writer;
 import java.util.Objects;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Writer implementation that writes the data to an {@link Appendable} Object.
  * <p>
@@ -124,10 +126,7 @@ public T getAppendable() {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
-        Objects.requireNonNull(cbuf, "cbuf");
-        if (len < 0 || off + len > cbuf.length) {
-            throw new IndexOutOfBoundsException("Array Size=" + cbuf.length + ", offset=" + off + ", length=" + len);
-        }
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         for (int i = 0; i < len; i++) {
             appendable.append(cbuf[off + i]);
         }
diff --git a/src/main/java/org/apache/commons/io/output/BrokenWriter.java b/src/main/java/org/apache/commons/io/output/BrokenWriter.java
index 7fe244d2392..1feac6bb84a 100644
--- a/src/main/java/org/apache/commons/io/output/BrokenWriter.java
+++ b/src/main/java/org/apache/commons/io/output/BrokenWriter.java
@@ -20,6 +20,7 @@
 import java.io.Writer;
 import java.util.function.Supplier;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.Erase;
 
 /**
@@ -121,6 +122,7 @@ private RuntimeException rethrow() {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         throw rethrow();
     }
 
diff --git a/src/main/java/org/apache/commons/io/output/ByteArrayOutputStream.java b/src/main/java/org/apache/commons/io/output/ByteArrayOutputStream.java
index b2a9afbfc58..48fb793669b 100644
--- a/src/main/java/org/apache/commons/io/output/ByteArrayOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ByteArrayOutputStream.java
@@ -21,6 +21,8 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Implements a ThreadSafe version of {@link AbstractByteArrayOutputStream} using instance synchronization.
  */
@@ -130,13 +132,7 @@ public synchronized InputStream toInputStream() {
 
     @Override
     public void write(final byte[] b, final int off, final int len) {
-        if (off < 0
-                || off > b.length
-                || len < 0
-                || off + len > b.length
-                || off + len < 0) {
-            throw new IndexOutOfBoundsException();
-        }
+        IOUtils.checkFromIndexSize(b, off, len);
         if (len == 0) {
             return;
         }
diff --git a/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java b/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
index 4612a7de2f7..adecd946a3e 100644
--- a/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
@@ -172,6 +172,7 @@ int getChunkSize() {
      */
     @Override
     public void write(final byte[] data, final int srcOffset, final int length) throws IOException {
+        IOUtils.checkFromIndexSize(data, srcOffset, length);
         int bytes = length;
         int dstOffset = srcOffset;
         while (bytes > 0) {
diff --git a/src/main/java/org/apache/commons/io/output/ChunkedWriter.java b/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
index 6a6492882b1..f18553fb776 100644
--- a/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
+++ b/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
@@ -74,6 +74,7 @@ public ChunkedWriter(final Writer writer, final int chunkSize) {
      */
     @Override
     public void write(final char[] data, final int srcOffset, final int length) throws IOException {
+        IOUtils.checkFromIndexSize(data, srcOffset, length);
         int bytes = length;
         int dstOffset = srcOffset;
         while (bytes > 0) {
diff --git a/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java b/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
index 18783481d44..faa342f40f6 100644
--- a/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
@@ -20,6 +20,8 @@
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Throws an IOException on all attempts to write to the stream.
  * <p>
@@ -73,6 +75,7 @@ public void flush() throws IOException {
      */
     @Override
     public void write(final byte b[], final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(b, off, len);
         throw new IOException("write(byte[], int, int) failed: stream is closed");
     }
 
diff --git a/src/main/java/org/apache/commons/io/output/ClosedWriter.java b/src/main/java/org/apache/commons/io/output/ClosedWriter.java
index 58c3993acd3..bc1add898ad 100644
--- a/src/main/java/org/apache/commons/io/output/ClosedWriter.java
+++ b/src/main/java/org/apache/commons/io/output/ClosedWriter.java
@@ -20,6 +20,8 @@
 import java.io.IOException;
 import java.io.Writer;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Throws an IOException on all attempts to write with {@link #close()} implemented as a noop.
  * <p>
@@ -77,6 +79,7 @@ public void flush() throws IOException {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         throw new IOException("write(" + new String(cbuf) + ", " + off + ", " + len + ") failed: stream is closed");
     }
 }
diff --git a/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java b/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
index d78f049e635..1a13d90eff3 100644
--- a/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
+++ b/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
@@ -28,6 +28,7 @@
 
 import org.apache.commons.io.IOExceptionList;
 import org.apache.commons.io.IOIndexedException;
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.IOConsumer;
 
 /**
@@ -128,6 +129,7 @@ public void write(final char[] cbuf) throws IOException {
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         forAllWriters(w -> w.write(cbuf, off, len));
     }
 
@@ -159,6 +161,7 @@ public void write(final String str) throws IOException {
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final String str, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(str, off, len);
         forAllWriters(w -> w.write(str, off, len));
     }
 
diff --git a/src/main/java/org/apache/commons/io/output/NullAppendable.java b/src/main/java/org/apache/commons/io/output/NullAppendable.java
index 520daa3a64b..fee5dace602 100644
--- a/src/main/java/org/apache/commons/io/output/NullAppendable.java
+++ b/src/main/java/org/apache/commons/io/output/NullAppendable.java
@@ -19,6 +19,8 @@
 
 import java.io.IOException;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Appends all data to the famous <strong>/dev/null</strong>.
  * <p>
@@ -51,6 +53,7 @@ public Appendable append(final CharSequence csq) throws IOException {
 
     @Override
     public Appendable append(final CharSequence csq, final int start, final int end) throws IOException {
+        IOUtils.checkFromToIndex(csq, start, end);
         return this;
     }
 
diff --git a/src/main/java/org/apache/commons/io/output/NullOutputStream.java b/src/main/java/org/apache/commons/io/output/NullOutputStream.java
index 5275aea9c75..682d0f8e768 100644
--- a/src/main/java/org/apache/commons/io/output/NullOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/NullOutputStream.java
@@ -19,6 +19,8 @@
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Never writes data. Calls never go beyond this class.
  * <p>
@@ -75,7 +77,7 @@ public void write(final byte[] b) throws IOException {
      */
     @Override
     public void write(final byte[] b, final int off, final int len) {
-        // noop
+        IOUtils.checkFromIndexSize(b, off, len);
     }
 
     /**
diff --git a/src/main/java/org/apache/commons/io/output/NullWriter.java b/src/main/java/org/apache/commons/io/output/NullWriter.java
index ab7f4ddd6f8..b209056d194 100644
--- a/src/main/java/org/apache/commons/io/output/NullWriter.java
+++ b/src/main/java/org/apache/commons/io/output/NullWriter.java
@@ -18,6 +18,8 @@
 
 import java.io.Writer;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * Never writes data. Calls never go beyond this class.
  * <p>
@@ -87,7 +89,7 @@ public Writer append(final CharSequence csq) {
      */
     @Override
     public Writer append(final CharSequence csq, final int start, final int end) {
-        //to /dev/null
+        IOUtils.checkFromToIndex(csq, start, end);
         return this;
     }
 
@@ -154,7 +156,7 @@ public void write(final String str) {
      */
     @Override
     public void write(final String str, final int st, final int end) {
-        //to /dev/null
+        IOUtils.checkFromIndexSize(str, st, end);
     }
 
 }
diff --git a/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java b/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
index 106525e88f9..836e8bc3753 100644
--- a/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
+++ b/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
@@ -20,6 +20,8 @@
 import java.io.StringWriter;
 import java.io.Writer;
 
+import org.apache.commons.io.IOUtils;
+
 /**
  * {@link Writer} implementation that outputs to a {@link StringBuilder}.
  * <p>
@@ -149,9 +151,8 @@ public String toString() {
      */
     @Override
     public void write(final char[] value, final int offset, final int length) {
-        if (value != null) {
-            builder.append(value, offset, length);
-        }
+        IOUtils.checkFromIndexSize(value, offset, length);
+        builder.append(value, offset, length);
     }
 
     /**
diff --git a/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java b/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
index e5892dbd885..2efe401910a 100644
--- a/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.IOConsumer;
 import org.apache.commons.io.function.IOFunction;
 
@@ -249,6 +250,7 @@ public void write(final byte[] b) throws IOException {
     @SuppressWarnings("resource") // the underlying stream is managed by a subclass.
     @Override
     public void write(final byte[] b, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(b, off, len);
         // TODO we could write the sub-array up the threshold, fire the event,
         // and then write the rest so the event is always fired at the precise point.
         checkThreshold(len);
diff --git a/src/main/java/org/apache/commons/io/output/UnsynchronizedByteArrayOutputStream.java b/src/main/java/org/apache/commons/io/output/UnsynchronizedByteArrayOutputStream.java
index f20ccefad74..a47a3b2aa2a 100644
--- a/src/main/java/org/apache/commons/io/output/UnsynchronizedByteArrayOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/UnsynchronizedByteArrayOutputStream.java
@@ -21,6 +21,7 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.build.AbstractOrigin;
 import org.apache.commons.io.build.AbstractStreamBuilder;
 import org.apache.commons.io.function.Uncheck;
@@ -214,9 +215,7 @@ public InputStream toInputStream() {
 
     @Override
     public void write(final byte[] b, final int off, final int len) {
-        if (off < 0 || off > b.length || len < 0 || off + len > b.length || off + len < 0) {
-            throw new IndexOutOfBoundsException(String.format("offset=%,d, length=%,d", off, len));
-        }
+        IOUtils.checkFromIndexSize(b, off, len);
         if (len == 0) {
             return;
         }
diff --git a/src/main/java/org/apache/commons/io/output/WriterOutputStream.java b/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
index dcb6e226e72..c753ccdce87 100644
--- a/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
@@ -448,6 +448,7 @@ public void write(final byte[] b) throws IOException {
      */
     @Override
     public void write(final byte[] b, int off, int len) throws IOException {
+        IOUtils.checkFromIndexSize(b, off, len);
         while (len > 0) {
             final int c = Math.min(len, decoderIn.remaining());
             decoderIn.put(b, off, c);
diff --git a/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java b/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
index 40fdcc8f730..73630a4bca2 100644
--- a/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
+++ b/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
@@ -306,6 +306,7 @@ public String getEncoding() {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         if (prologWriter != null) {
             detectEncoding(cbuf, off, len);
         } else {
diff --git a/src/test/java/org/apache/commons/io/IOUtilsTest.java b/src/test/java/org/apache/commons/io/IOUtilsTest.java
index d062ae61ea8..02574946bf8 100644
--- a/src/test/java/org/apache/commons/io/IOUtilsTest.java
+++ b/src/test/java/org/apache/commons/io/IOUtilsTest.java
@@ -400,6 +400,56 @@ void testCheckFromIndexSizeInvalidCases(int off, int len, int arrayLength) {
         }
     }
 
+    static Stream<Arguments> testCheckFromToIndexValidCases() {
+        return Stream.of(
+                // Valid cases
+                Arguments.of(0, 0, 42),
+                Arguments.of(0, 1, 42),
+                Arguments.of(0, 42, 42),
+                Arguments.of(41, 42, 42),
+                Arguments.of(42, 42, 42)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void testCheckFromToIndexValidCases(int from, int to, int arrayLength) {
+        assertDoesNotThrow(() -> IOUtils.checkFromToIndex(from, to, arrayLength));
+    }
+
+    static Stream<Arguments> testCheckFromToIndexInvalidCases() {
+        return Stream.of(
+                Arguments.of(-1, 0, 42),
+                Arguments.of(0, -1, 42),
+                Arguments.of(0, 0, -1),
+                // from > to
+                Arguments.of(1, 0, 42),
+                // to > arrayLength
+                Arguments.of(0, 43, 42),
+                Arguments.of(1, 43, 42)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void testCheckFromToIndexInvalidCases(int from, int to, int arrayLength) {
+        final IndexOutOfBoundsException ex = assertThrows(IndexOutOfBoundsException.class, () -> IOUtils.checkFromToIndex(from, to, arrayLength));
+        assertTrue(ex.getMessage().contains(String.valueOf(from)));
+        assertTrue(ex.getMessage().contains(String.valueOf(to)));
+        assertTrue(ex.getMessage().contains(String.valueOf(arrayLength)));
+        // Optional requirement: compare the exception message for Java 8 and Java 9+
+        if (SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_9)) {
+            final IndexOutOfBoundsException jreEx = assertThrows(IndexOutOfBoundsException.class, () -> {
+                try {
+                    Objects.class.getDeclaredMethod("checkFromToIndex", int.class, int.class, int.class).invoke(null, from, to, arrayLength);
+                } catch (InvocationTargetException ite) {
+                    throw ite.getTargetException();
+                }
+            });
+            assertEquals(jreEx.getMessage(), ex.getMessage());
+        }
+    }
+
     @Test
     void testClose() {
         assertDoesNotThrow(() -> IOUtils.close((Closeable) null));

From 051a86a3c28eece62e8008c31435e274d7ef342e Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Mon, 29 Sep 2025 10:26:44 +0200
Subject: [PATCH 04/25] fix: failing tests

---
 .../java/org/apache/commons/io/IOUtils.java   |  6 ++-
 .../input/UnsynchronizedBufferedReader.java   |  7 ++-
 .../apache/commons/io/output/NullWriter.java  | 12 ++++--
 .../io/input/ClosedInputStreamTest.java       |  5 ++-
 .../commons/io/input/ClosedReaderTest.java    |  6 +--
 .../io/input/MarkShieldInputStreamTest.java   |  2 +-
 .../commons/io/input/NullInputStreamTest.java |  2 +-
 .../commons/io/input/ProxyReaderTest.java     |  5 +++
 .../UnsynchronizedBufferedReaderTest.java     | 43 +++++++++++++------
 .../io/output/ByteArrayOutputStreamTest.java  |  2 +-
 .../commons/io/output/NullAppendableTest.java |  7 ++-
 .../commons/io/output/ProxyWriterTest.java    |  9 ++--
 12 files changed, 73 insertions(+), 33 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index 0d671eac9ee..11d1585309d 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -496,9 +496,11 @@ static void checkFromIndexSize(final int off, final int len, final int arrayLeng
      *     <li>{@code toIndex <= seq.length()}</li>
      * </ul>
      *
+     * <p>If {@code seq} is null, it is treated as the string "null".</p>
+     *
      * <p>If the range is invalid, this method throws an {@link IndexOutOfBoundsException} with a descriptive message.</p>
      *
-     * @param seq The char sequence to be checked against
+     * @param seq The char sequence to be checked against, may be {@code null}
      * @param fromIndex The starting index into the char sequence (inclusive)
      * @param toIndex The ending index into the char sequence (exclusive)
      * @throws NullPointerException If the char sequence is null
@@ -506,7 +508,7 @@ static void checkFromIndexSize(final int off, final int len, final int arrayLeng
      * @since 2.21.0
      */
     public static void checkFromToIndex(final CharSequence seq, int fromIndex, final int toIndex) {
-        checkFromToIndex(fromIndex, toIndex, requireNonNull(seq, "char sequence").length());
+        checkFromToIndex(fromIndex, toIndex, seq != null ? seq.length() : 4);
     }
 
     static void checkFromToIndex(final int fromIndex, final int toIndex, final int length) {
diff --git a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
index e8bf3363f05..bde55873f24 100644
--- a/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
+++ b/src/main/java/org/apache/commons/io/input/UnsynchronizedBufferedReader.java
@@ -271,11 +271,16 @@ public int read() throws IOException {
      */
     @Override
     public int read(final char[] buffer, int offset, final int length) throws IOException {
+        /*
+         * First throw on a closed reader, then check the parameters.
+         *
+         * This behavior is not specified in the Javadoc, but is followed by most readers in java.io.
+         */
+        checkOpen();
         IOUtils.checkFromIndexSize(buffer, offset, length);
         if (length == 0) {
             return 0;
         }
-        checkOpen();
 
         int outstanding = length;
         while (outstanding > 0) {
diff --git a/src/main/java/org/apache/commons/io/output/NullWriter.java b/src/main/java/org/apache/commons/io/output/NullWriter.java
index b209056d194..9741b819766 100644
--- a/src/main/java/org/apache/commons/io/output/NullWriter.java
+++ b/src/main/java/org/apache/commons/io/output/NullWriter.java
@@ -112,6 +112,7 @@ public void flush() {
      */
     @Override
     public void write(final char[] chr) {
+        write(chr, 0, chr.length);
         //to /dev/null
     }
 
@@ -124,6 +125,7 @@ public void write(final char[] chr) {
      */
     @Override
     public void write(final char[] chr, final int st, final int end) {
+        IOUtils.checkFromIndexSize(chr, st, end);
         //to /dev/null
     }
 
@@ -144,6 +146,7 @@ public void write(final int b) {
      */
     @Override
     public void write(final String str) {
+        write(str, 0, str.length());
         //to /dev/null
     }
 
@@ -151,12 +154,13 @@ public void write(final String str) {
      * Does nothing, like writing to {@code /dev/null}.
      *
      * @param str The string to write.
-     * @param st The start offset.
-     * @param end The number of characters to write.
+     * @param off The start offset.
+     * @param len The number of characters to write.
      */
     @Override
-    public void write(final String str, final int st, final int end) {
-        IOUtils.checkFromIndexSize(str, st, end);
+    public void write(final String str, final int off, final int len) {
+        IOUtils.checkFromIndexSize(str, off, len);
+        //to /dev/null
     }
 
 }
diff --git a/src/test/java/org/apache/commons/io/input/ClosedInputStreamTest.java b/src/test/java/org/apache/commons/io/input/ClosedInputStreamTest.java
index b19364d8a17..2586806b3a5 100644
--- a/src/test/java/org/apache/commons/io/input/ClosedInputStreamTest.java
+++ b/src/test/java/org/apache/commons/io/input/ClosedInputStreamTest.java
@@ -22,6 +22,7 @@
 
 import java.io.InputStream;
 
+import org.apache.commons.io.IOUtils;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -86,7 +87,7 @@ void testReadArray() throws Exception {
         try (ClosedInputStream cis = new ClosedInputStream()) {
             assertEquals(EOF, cis.read(new byte[4096]));
             assertEquals(EOF, cis.read(new byte[1]));
-            assertEquals(EOF, cis.read(new byte[0]));
+            assertEquals(0, cis.read(IOUtils.EMPTY_BYTE_ARRAY));
         }
     }
 
@@ -95,7 +96,7 @@ void testReadArrayIndex() throws Exception {
         try (ClosedInputStream cis = new ClosedInputStream()) {
             assertEquals(EOF, cis.read(new byte[4096], 0, 1));
             assertEquals(EOF, cis.read(new byte[1], 0, 1));
-            assertEquals(EOF, cis.read(new byte[0], 0, 0));
+            assertEquals(0, cis.read(IOUtils.EMPTY_BYTE_ARRAY, 0, 0));
         }
     }
 
diff --git a/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java b/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
index cb57f9e6f91..891049f9ef5 100644
--- a/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
@@ -46,7 +46,7 @@ void testReadArray() throws Exception {
         try (Reader reader = new ClosedReader()) {
             assertEquals(EOF, reader.read(new char[4096]));
             assertEquals(EOF, reader.read(new char[1]));
-            assertEquals(EOF, reader.read(new char[0]));
+            assertEquals(0, reader.read(new char[0]));
         }
     }
 
@@ -55,7 +55,7 @@ void testReadArrayIndex() throws Exception {
         try (Reader reader = new ClosedReader()) {
             assertEquals(EOF, reader.read(CharBuffer.wrap(new char[4096])));
             assertEquals(EOF, reader.read(CharBuffer.wrap(new char[1])));
-            assertEquals(EOF, reader.read(CharBuffer.wrap(new char[0])));
+            assertEquals(0, reader.read(CharBuffer.wrap(new char[0])));
         }
     }
 
@@ -64,7 +64,7 @@ void testReadCharBuffer() throws Exception {
         try (Reader reader = new ClosedReader()) {
             assertEquals(EOF, reader.read(new char[4096]));
             assertEquals(EOF, reader.read(new char[1]));
-            assertEquals(EOF, reader.read(new char[0]));
+            assertEquals(0, reader.read(new char[0]));
         }
     }
 
diff --git a/src/test/java/org/apache/commons/io/input/MarkShieldInputStreamTest.java b/src/test/java/org/apache/commons/io/input/MarkShieldInputStreamTest.java
index a1e4d17f457..2566f8b51e6 100644
--- a/src/test/java/org/apache/commons/io/input/MarkShieldInputStreamTest.java
+++ b/src/test/java/org/apache/commons/io/input/MarkShieldInputStreamTest.java
@@ -152,7 +152,7 @@ void testReadByteArrayIntIntAfterClose(final int len) throws Exception {
                 MarkShieldInputStream msis = new MarkShieldInputStream(in)) {
             assertEquals(len, in.available());
             in.close();
-            assertEquals(0, in.read(new byte[0], 0, 1));
+            assertThrows(IndexOutOfBoundsException.class, () -> in.read(new byte[0], 0, 1));
             assertEquals(0, in.read(new byte[1], 0, 0));
             assertThrows(IOException.class, () -> in.read(new byte[2], 0, 1));
         }
diff --git a/src/test/java/org/apache/commons/io/input/NullInputStreamTest.java b/src/test/java/org/apache/commons/io/input/NullInputStreamTest.java
index b79555d8c02..9b59ac90c0e 100644
--- a/src/test/java/org/apache/commons/io/input/NullInputStreamTest.java
+++ b/src/test/java/org/apache/commons/io/input/NullInputStreamTest.java
@@ -249,7 +249,7 @@ void testReadByteArrayIntIntAfterClose() throws Exception {
         try (InputStream in = new NullInputStream()) {
             assertEquals(0, in.available());
             in.close();
-            assertEquals(0, in.read(new byte[0], 0, 1));
+            assertThrows(IndexOutOfBoundsException.class, () -> in.read(new byte[0], 0, 1));
             assertEquals(0, in.read(new byte[1], 0, 0));
             assertThrows(IOException.class, () -> in.read(new byte[2], 0, 1));
         }
diff --git a/src/test/java/org/apache/commons/io/input/ProxyReaderTest.java b/src/test/java/org/apache/commons/io/input/ProxyReaderTest.java
index f33979ce1b8..681ab90eae0 100644
--- a/src/test/java/org/apache/commons/io/input/ProxyReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/ProxyReaderTest.java
@@ -38,6 +38,11 @@ public int read(final char[] chars) throws IOException {
             return chars == null ? 0 : super.read(chars);
         }
 
+        @Override
+        public int read(final char[] chars, final int offset, final int length) throws IOException {
+            return chars == null ? 0 : super.read(chars, offset, length);
+        }
+
         @Override
         public int read(final CharBuffer target) throws IOException {
             return target == null ? 0 : super.read(target);
diff --git a/src/test/java/org/apache/commons/io/input/UnsynchronizedBufferedReaderTest.java b/src/test/java/org/apache/commons/io/input/UnsynchronizedBufferedReaderTest.java
index 9c7dbf6fd81..a144bc418d0 100644
--- a/src/test/java/org/apache/commons/io/input/UnsynchronizedBufferedReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/UnsynchronizedBufferedReaderTest.java
@@ -353,35 +353,46 @@ void testRead() throws IOException {
      * @throws IOException test failure.
      */
     @Test
-    void testReadArray() throws IOException {
+    void testReadArray1() throws IOException {
         final char[] ca = new char[2];
         try (UnsynchronizedBufferedReader toRet = new UnsynchronizedBufferedReader(new InputStreamReader(new ByteArrayInputStream(new byte[0])))) {
-            /* Null buffer should throw NPE even when len == 0 */
+            /* Validate parameters, before returning 0 */
             assertThrows(NullPointerException.class, () -> toRet.read(null, 1, 0));
+            assertThrows(IndexOutOfBoundsException.class, () -> toRet.read(ca, 1, 5));
+            /* Read zero bytes should return 0 */
+            assertEquals(0, toRet.read(ca, 0, 0));
             toRet.close();
-            assertThrows(IOException.class, () -> toRet.read(null, 1, 0));
-            /* Closed reader should throw IOException reading zero bytes */
-            assertThrows(IOException.class, () -> toRet.read(ca, 0, 0));
             /*
-             * Closed reader should throw IOException in preference to index out of bounds
+             * After close, readers in java.io consistently throw IOException before checking parameters or returning 0.
              */
-            // Read should throw IOException before
-            // ArrayIndexOutOfBoundException
+            assertThrows(IOException.class, () -> toRet.read(null, 1, 0));
             assertThrows(IOException.class, () -> toRet.read(ca, 1, 5));
+            assertThrows(IOException.class, () -> toRet.read(ca, 0, 0));
         }
+    }
+
+    @Test
+    void testReadArray2() throws IOException {
+        final char[] ca = new char[2];
         // Test to ensure that a drained stream returns 0 at EOF
         try (UnsynchronizedBufferedReader toRet2 = new UnsynchronizedBufferedReader(new InputStreamReader(new ByteArrayInputStream(new byte[2])))) {
             assertEquals(2, toRet2.read(ca, 0, 2));
             assertEquals(-1, toRet2.read(ca, 0, 2));
             assertEquals(0, toRet2.read(ca, 0, 0));
         }
+    }
 
+    @Test
+    void testReadArray3() throws IOException {
         // Test for method int UnsynchronizedBufferedReader.read(char [], int, int)
         final char[] buf = new char[testString.length()];
         br = new UnsynchronizedBufferedReader(new StringReader(testString));
         br.read(buf, 50, 500);
         assertTrue(new String(buf, 50, 500).equals(testString.substring(0, 500)));
+    }
 
+    @Test
+    void testReadArray4() throws IOException {
         try (UnsynchronizedBufferedReader bufin = new UnsynchronizedBufferedReader(new Reader() {
             int size = 2;
             int pos;
@@ -424,11 +435,18 @@ public boolean ready() throws IOException {
             final int result = bufin.read(new char[2], 0, 2);
             assertEquals(result, 1);
         }
+    }
+
+    @Test
+    void testReadArray_HARMONY_831() throws IOException {
         // regression for HARMONY-831
         try (Reader reader = new UnsynchronizedBufferedReader(new PipedReader(), 9)) {
             assertThrows(IndexOutOfBoundsException.class, () -> reader.read(new char[] {}, 7, 0));
         }
+    }
 
+    @Test
+    void testReadArray_HARMONY_54() throws IOException {
         // Regression for HARMONY-54
         final char[] ch = {};
         @SuppressWarnings("resource")
@@ -456,13 +474,12 @@ void testReadArrayException() throws IOException {
         br = new UnsynchronizedBufferedReader(new StringReader(testString));
         final char[] nullCharArray = null;
         final char[] charArray = testString.toCharArray();
-        assertThrows(IndexOutOfBoundsException.class, () -> br.read(nullCharArray, -1, -1));
-        assertThrows(IndexOutOfBoundsException.class, () -> br.read(nullCharArray, -1, 0));
+        assertThrows(NullPointerException.class, () -> br.read(nullCharArray, -1, 0));
         assertThrows(NullPointerException.class, () -> br.read(nullCharArray, 0, -1));
-        assertThrows(NullPointerException.class, () -> br.read(nullCharArray, 0, 0));
-        assertThrows(NullPointerException.class, () -> br.read(nullCharArray, 0, 1));
-        assertThrows(IndexOutOfBoundsException.class, () -> br.read(charArray, -1, -1));
+        assertThrows(NullPointerException.class, () -> br.read(nullCharArray, 1, 1));
         assertThrows(IndexOutOfBoundsException.class, () -> br.read(charArray, -1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> br.read(charArray, 0, -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> br.read(charArray, charArray.length, 1));
 
         br.read(charArray, 0, 0);
         br.read(charArray, 0, charArray.length);
diff --git a/src/test/java/org/apache/commons/io/output/ByteArrayOutputStreamTest.java b/src/test/java/org/apache/commons/io/output/ByteArrayOutputStreamTest.java
index fa19ba2a41a..9bae1cb5f62 100644
--- a/src/test/java/org/apache/commons/io/output/ByteArrayOutputStreamTest.java
+++ b/src/test/java/org/apache/commons/io/output/ByteArrayOutputStreamTest.java
@@ -177,7 +177,7 @@ void testInvalidWriteOffsetOver(final String baosName, final BAOSFactory<?> baos
     @MethodSource("baosFactories")
     void testInvalidWriteOffsetUnder(final String baosName, final BAOSFactory<?> baosFactory) throws IOException {
         try (AbstractByteArrayOutputStream<?> baout = baosFactory.newInstance()) {
-            assertThrows(IndexOutOfBoundsException.class, () -> baout.write(null, -1, 0));
+            assertThrows(IndexOutOfBoundsException.class, () -> baout.write(IOUtils.EMPTY_BYTE_ARRAY, -1, 0));
         }
     }
 
diff --git a/src/test/java/org/apache/commons/io/output/NullAppendableTest.java b/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
index 6caa15023d9..09b1d1bf2ba 100644
--- a/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
+++ b/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
@@ -16,6 +16,8 @@
  */
 package org.apache.commons.io.output;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import java.io.IOException;
 
 import org.junit.jupiter.api.Test;
@@ -32,7 +34,10 @@ void testNull() throws IOException {
         appendable.append("A");
         appendable.append("A", 0, 1);
         appendable.append(null, 0, 1);
-        appendable.append(null, -1, -1);
+        // `null` is converted to "null"
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, -1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, 1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, 0, 5));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/io/output/ProxyWriterTest.java b/src/test/java/org/apache/commons/io/output/ProxyWriterTest.java
index 9954ca06803..e810d39d726 100644
--- a/src/test/java/org/apache/commons/io/output/ProxyWriterTest.java
+++ b/src/test/java/org/apache/commons/io/output/ProxyWriterTest.java
@@ -205,8 +205,8 @@ public void write(final String str, final int off, final int len) throws IOExcep
     @Test
     void testNullCharArray() throws Exception {
         try (ProxyWriter proxy = new ProxyWriter(NullWriter.INSTANCE)) {
-            proxy.write((char[]) null);
-            proxy.write((char[]) null, 0, 0);
+            assertThrows(NullPointerException.class, () -> proxy.write((char[]) null));
+            assertThrows(NullPointerException.class, () -> proxy.write((char[]) null, 0, 0));
         }
     }
 
@@ -220,8 +220,9 @@ void testNullCharSequence() throws Exception {
     @Test
     void testNullString() throws Exception {
         try (ProxyWriter proxy = new ProxyWriter(NullWriter.INSTANCE)) {
-            proxy.write((String) null);
-            proxy.write((String) null, 0, 0);
+            // Default implementation delegates to write(char[], int, int)
+            assertThrows(NullPointerException.class, () -> proxy.write((String) null));
+            assertThrows(NullPointerException.class, () -> proxy.write((String) null, 0, 0));
         }
     }
 

From cbfb55cc15c3f4344bbe7079026b0214024b11e9 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Mon, 29 Sep 2025 10:27:20 +0200
Subject: [PATCH 05/25] fix: inline static import

---
 .../java/org/apache/commons/io/IOUtils.java   | 32 +++++++++----------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index 11d1585309d..d1d01573698 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -17,8 +17,6 @@
 
 package org.apache.commons.io;
 
-import static java.util.Objects.requireNonNull;
-
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
@@ -246,7 +244,7 @@ public class IOUtils {
     public static BufferedInputStream buffer(final InputStream inputStream) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        requireNonNull(inputStream, "inputStream");
+        Objects.requireNonNull(inputStream, "inputStream");
         return inputStream instanceof BufferedInputStream ?
                 (BufferedInputStream) inputStream : new BufferedInputStream(inputStream);
     }
@@ -265,7 +263,7 @@ public static BufferedInputStream buffer(final InputStream inputStream) {
     public static BufferedInputStream buffer(final InputStream inputStream, final int size) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        requireNonNull(inputStream, "inputStream");
+        Objects.requireNonNull(inputStream, "inputStream");
         return inputStream instanceof BufferedInputStream ?
                 (BufferedInputStream) inputStream : new BufferedInputStream(inputStream, size);
     }
@@ -283,7 +281,7 @@ public static BufferedInputStream buffer(final InputStream inputStream, final in
     public static BufferedOutputStream buffer(final OutputStream outputStream) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        requireNonNull(outputStream, "outputStream");
+        Objects.requireNonNull(outputStream, "outputStream");
         return outputStream instanceof BufferedOutputStream ?
                 (BufferedOutputStream) outputStream : new BufferedOutputStream(outputStream);
     }
@@ -302,7 +300,7 @@ public static BufferedOutputStream buffer(final OutputStream outputStream) {
     public static BufferedOutputStream buffer(final OutputStream outputStream, final int size) {
         // reject null early on rather than waiting for IO operation to fail
         // not checked by BufferedInputStream
-        requireNonNull(outputStream, "outputStream");
+        Objects.requireNonNull(outputStream, "outputStream");
         return outputStream instanceof BufferedOutputStream ?
                 (BufferedOutputStream) outputStream : new BufferedOutputStream(outputStream, size);
     }
@@ -429,7 +427,7 @@ private static char[] charArray(final int size) {
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final byte[] array, final int off, final int len) {
-        checkFromIndexSize(off, len, requireNonNull(array, "byte array").length);
+        checkFromIndexSize(off, len, Objects.requireNonNull(array, "byte array").length);
     }
 
     /**
@@ -453,7 +451,7 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final char[] array, final int off, final int len) {
-        checkFromIndexSize(off, len, requireNonNull(array, "char array").length);
+        checkFromIndexSize(off, len, Objects.requireNonNull(array, "char array").length);
     }
 
     /**
@@ -477,7 +475,7 @@ public static void checkFromIndexSize(final char[] array, final int off, final i
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final String str, final int off, final int len) {
-        checkFromIndexSize(off, len, requireNonNull(str, "str").length());
+        checkFromIndexSize(off, len, Objects.requireNonNull(str, "str").length());
     }
 
     static void checkFromIndexSize(final int off, final int len, final int arrayLength) {
@@ -1298,7 +1296,7 @@ public static void copy(final InputStream input, final Writer writer, final Stri
      */
     @SuppressWarnings("resource") // streams are closed by the caller.
     public static QueueInputStream copy(final java.io.ByteArrayOutputStream outputStream) throws IOException {
-        requireNonNull(outputStream, "outputStream");
+        Objects.requireNonNull(outputStream, "outputStream");
         final QueueInputStream in = new QueueInputStream();
         outputStream.writeTo(in.newQueueOutputStream());
         return in;
@@ -1479,7 +1477,7 @@ public static int copy(final Reader reader, final Writer writer) throws IOExcept
      * @since 2.9.0
      */
     public static long copy(final URL url, final File file) throws IOException {
-        try (OutputStream outputStream = Files.newOutputStream(requireNonNull(file, "file").toPath())) {
+        try (OutputStream outputStream = Files.newOutputStream(Objects.requireNonNull(file, "file").toPath())) {
             return copy(url, outputStream);
         }
     }
@@ -1502,7 +1500,7 @@ public static long copy(final URL url, final File file) throws IOException {
      * @since 2.9.0
      */
     public static long copy(final URL url, final OutputStream outputStream) throws IOException {
-        try (InputStream inputStream = requireNonNull(url, "url").openStream()) {
+        try (InputStream inputStream = Objects.requireNonNull(url, "url").openStream()) {
             return copyLarge(inputStream, outputStream);
         }
     }
@@ -1551,8 +1549,8 @@ public static long copyLarge(final InputStream inputStream, final OutputStream o
     @SuppressWarnings("resource") // streams are closed by the caller.
     public static long copyLarge(final InputStream inputStream, final OutputStream outputStream, final byte[] buffer)
         throws IOException {
-        requireNonNull(inputStream, "inputStream");
-        requireNonNull(outputStream, "outputStream");
+        Objects.requireNonNull(inputStream, "inputStream");
+        Objects.requireNonNull(outputStream, "outputStream");
         long count = 0;
         int n;
         while (EOF != (n = inputStream.read(buffer))) {
@@ -2820,7 +2818,7 @@ public static byte[] toByteArray(final InputStream inputStream) throws IOExcepti
      * @since 2.1
      */
     public static byte[] toByteArray(final InputStream input, final int size) throws IOException {
-        return toByteArray(requireNonNull(input, "input")::read, size);
+        return toByteArray(Objects.requireNonNull(input, "input")::read, size);
     }
 
     /**
@@ -2846,7 +2844,7 @@ public static byte[] toByteArray(final InputStream input, final int size) throws
      * @since 2.21.0
      */
     public static byte[] toByteArray(final InputStream input, final int size, final int chunkSize) throws IOException {
-        requireNonNull(input, "input");
+        Objects.requireNonNull(input, "input");
         if (chunkSize <= 0) {
             throw new IllegalArgumentException("Chunk size must be greater than zero: " + chunkSize);
         }
@@ -3994,7 +3992,7 @@ public static void writeLines(final Collection<?> lines, String lineEnding, fina
      * @since 2.7
      */
     public static Writer writer(final Appendable appendable) {
-        requireNonNull(appendable, "appendable");
+        Objects.requireNonNull(appendable, "appendable");
         if (appendable instanceof Writer) {
             return (Writer) appendable;
         }

From 8b45ad9176a664df45fb939269e42edd58ac3b3d Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Mon, 29 Sep 2025 10:54:20 +0200
Subject: [PATCH 06/25] fix: add usage examples to Javadoc

---
 .../java/org/apache/commons/io/IOUtils.java   | 150 +++++++++++++-----
 1 file changed, 112 insertions(+), 38 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index d1d01573698..bf685c435f2 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -407,7 +407,7 @@ private static char[] charArray(final int size) {
     }
 
     /**
-     * Checks if the sub-range described by an offset and length is valid for the given array.
+     * Validates that the sub-range {@code [off, off + len)} is within the bounds of the given array.
      *
      * <p>The range is valid if all of the following hold:</p>
      * <ul>
@@ -416,14 +416,39 @@ private static char[] charArray(final int size) {
      *   <li>{@code off + len <= array.length}</li>
      * </ul>
      *
-     * <p>If the range is invalid, this method throws an
-     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     * <p>If the range is invalid, throws {@link IndexOutOfBoundsException} with a descriptive message.</p>
      *
-     * @param array       The array to be checked against
-     * @param off         The starting offset into the array
-     * @param len         The number of elements in the range
-     * @throws NullPointerException      If the array is null
-     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
+     * <p>Typical usage in {@link InputStream#read(byte[], int, int)} and {@link OutputStream#write(byte[], int, int)} implementations:</p>
+     *
+     * <pre>{@code
+     * @Override
+     * public int read(byte[] b, int off, int len) throws IOException {
+     *     IOUtils.checkFromIndexSize(b, off, len);
+     *     if (len == 0) {
+     *         return 0;
+     *     }
+     *     ensureOpen();
+     *     // perform read...
+     * }
+     *
+     * @Override
+     * public void write(byte[] b, int off, int len) throws IOException {
+     *     IOUtils.checkFromIndexSize(b, off, len);
+     *     if (len == 0) {
+     *         return;
+     *     }
+     *     ensureOpen();
+     *     // perform write...
+     * }
+     * }</pre>
+     *
+     * @param array the array against which the range is validated
+     * @param off   the starting offset into the array (inclusive)
+     * @param len   the number of elements to access
+     * @throws NullPointerException      if {@code array} is {@code null}
+     * @throws IndexOutOfBoundsException if the range {@code [off, off + len)} is out of bounds for {@code array}
+     * @see InputStream#read(byte[], int, int)
+     * @see OutputStream#write(byte[], int, int)
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final byte[] array, final int off, final int len) {
@@ -431,7 +456,7 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
     }
 
     /**
-     * Checks if the sub-range described by an offset and length is valid for the given array.
+     * Validates that the sub-range {@code [off, off + len)} is within the bounds of the given array.
      *
      * <p>The range is valid if all of the following hold:</p>
      * <ul>
@@ -440,14 +465,39 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      *   <li>{@code off + len <= array.length}</li>
      * </ul>
      *
-     * <p>If the range is invalid, this method throws an
-     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     * <p>If the range is invalid, throws {@link IndexOutOfBoundsException} with a descriptive message.</p>
      *
-     * @param array       The array to be checked against
-     * @param off         The starting offset into the array
-     * @param len         The number of elements in the range
-     * @throws NullPointerException      If the array is null
-     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
+     * <p>Typical usage in {@link Reader#read(char[], int, int)} and {@link Writer#write(char[], int, int)} implementations:</p>
+     *
+     * <pre>{@code
+     * @Override
+     * public int read(char[] cbuf, int off, int len) throws IOException {
+     *     ensureOpen();
+     *     IOUtils.checkFromIndexSize(cbuf, off, len);
+     *     if (len == 0) {
+     *         return 0;
+     *     }
+     *     // perform read...
+     * }
+     *
+     * @Override
+     * public void write(char[] cbuf, int off, int len) throws IOException {
+     *     ensureOpen();
+     *     IOUtils.checkFromIndexSize(cbuf, off, len);
+     *     if (len == 0) {
+     *         return;
+     *     }
+     *     // perform write...
+     * }
+     * }</pre>
+     *
+     * @param array the array against which the range is validated
+     * @param off   the starting offset into the array (inclusive)
+     * @param len   the number of characters to access
+     * @throws NullPointerException      if {@code array} is {@code null}
+     * @throws IndexOutOfBoundsException if the range {@code [off, off + len)} is out of bounds for {@code array}
+     * @see Reader#read(char[], int, int)
+     * @see Writer#write(char[], int, int)
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final char[] array, final int off, final int len) {
@@ -455,23 +505,36 @@ public static void checkFromIndexSize(final char[] array, final int off, final i
     }
 
     /**
-     * Checks if the sub-range described by an offset and length is valid for the given string.
+     * Validates that the sub-range {@code [off, off + len)} is within the bounds of the given string.
      *
      * <p>The range is valid if all of the following hold:</p>
      * <ul>
      *   <li>{@code off >= 0}</li>
      *   <li>{@code len >= 0}</li>
-     *   <li>{@code off + len <= array.length}</li>
+     *   <li>{@code off + len <= str.length()}</li>
      * </ul>
      *
-     * <p>If the range is invalid, this method throws an
-     * {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     * <p>If the range is invalid, throws {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     *
+     * <p>Typical usage in {@link Writer#write(String, int, int)} implementations:</p>
      *
-     * @param str         The char sequence to be checked against
-     * @param off         The starting offset into the array
-     * @param len         The number of elements in the range
-     * @throws NullPointerException      If the array is null
-     * @throws IndexOutOfBoundsException If the range {@code [off, off + len)} is out of bounds
+     * <pre>{@code
+     * @Override
+     * public void write(String str, int off, int len) throws IOException {
+     *     IOUtils.checkFromIndexSize(str, off, len);
+     *     if (len == 0) {
+     *         return;
+     *     }
+     *     // perform write...
+     * }
+     * }</pre>
+     *
+     * @param str the string against which the range is validated
+     * @param off the starting offset into the string (inclusive)
+     * @param len the number of characters to write
+     * @throws NullPointerException      if {@code str} is {@code null}
+     * @throws IndexOutOfBoundsException if the range {@code [off, off + len)} is out of bounds for {@code str}
+     * @see Writer#write(String, int, int)
      * @since 2.21.0
      */
     public static void checkFromIndexSize(final String str, final int off, final int len) {
@@ -485,27 +548,38 @@ static void checkFromIndexSize(final int off, final int len, final int arrayLeng
     }
 
     /**
-     * Checks if the sub-sequence described by fromIndex (inclusive) and toIndex (exclusive) is valid for the given {@link CharSequence}.
+     * Validates that the sub-sequence {@code [fromIndex, toIndex)} is within the bounds of the given {@link CharSequence}.
      *
-     * <p>The range is valid if all of the following hold:</p>
+     * <p>The sub-sequence is valid if all of the following hold:</p>
      * <ul>
-     *     <li>{@code fromIndex >= 0}</li>
-     *     <li>{@code fromIndex <= toIndex}</li>
-     *     <li>{@code toIndex <= seq.length()}</li>
+     *   <li>{@code fromIndex >= 0}</li>
+     *   <li>{@code fromIndex <= toIndex}</li>
+     *   <li>{@code toIndex <= seq.length()}</li>
      * </ul>
      *
-     * <p>If {@code seq} is null, it is treated as the string "null".</p>
+     * <p>If {@code seq} is {@code null}, it is treated as the literal string {@code "null"} (length {@code 4}).</p>
      *
-     * <p>If the range is invalid, this method throws an {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     * <p>If the range is invalid, throws {@link IndexOutOfBoundsException} with a descriptive message.</p>
+     *
+     * <p>Typical usage in {@link Appendable#append(CharSequence, int, int)} implementations:</p>
+     *
+     * <pre>{@code
+     * @Override
+     * public Appendable append(CharSequence csq, int start, int end) throws IOException {
+     *     IOUtils.checkFromToIndex(csq, start, end);
+     *     // perform append...
+     *     return this;
+     * }
+     * }</pre>
      *
-     * @param seq The char sequence to be checked against, may be {@code null}
-     * @param fromIndex The starting index into the char sequence (inclusive)
-     * @param toIndex The ending index into the char sequence (exclusive)
-     * @throws NullPointerException If the char sequence is null
-     * @throws IndexOutOfBoundsException If the range {@code [fromIndex, toIndex)} is out of bounds
+     * @param seq       the character sequence to validate (may be {@code null}, treated as {@code "null"})
+     * @param fromIndex the starting index (inclusive)
+     * @param toIndex   the ending index (exclusive)
+     * @throws IndexOutOfBoundsException if the range {@code [fromIndex, toIndex)} is out of bounds for {@code seq}
+     * @see Appendable#append(CharSequence, int, int)
      * @since 2.21.0
      */
-    public static void checkFromToIndex(final CharSequence seq, int fromIndex, final int toIndex) {
+    public static void checkFromToIndex(final CharSequence seq, final int fromIndex, final int toIndex) {
         checkFromToIndex(fromIndex, toIndex, seq != null ? seq.length() : 4);
     }
 

From 2220753dc30034d8bbc8ecadb12c92757264d71f Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Mon, 29 Sep 2025 11:13:31 +0200
Subject: [PATCH 07/25] fix: Javadoc for JDK 8 and 11

---
 .../java/org/apache/commons/io/IOUtils.java   | 28 +++++++++----------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index bf685c435f2..09c48f139d0 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -420,8 +420,8 @@ private static char[] charArray(final int size) {
      *
      * <p>Typical usage in {@link InputStream#read(byte[], int, int)} and {@link OutputStream#write(byte[], int, int)} implementations:</p>
      *
-     * <pre>{@code
-     * @Override
+     * <pre><code>
+     * {@code @Override}
      * public int read(byte[] b, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(b, off, len);
      *     if (len == 0) {
@@ -431,7 +431,7 @@ private static char[] charArray(final int size) {
      *     // perform read...
      * }
      *
-     * @Override
+     * {@code @Override}
      * public void write(byte[] b, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(b, off, len);
      *     if (len == 0) {
@@ -440,7 +440,7 @@ private static char[] charArray(final int size) {
      *     ensureOpen();
      *     // perform write...
      * }
-     * }</pre>
+     * </code></pre>
      *
      * @param array the array against which the range is validated
      * @param off   the starting offset into the array (inclusive)
@@ -469,8 +469,8 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      *
      * <p>Typical usage in {@link Reader#read(char[], int, int)} and {@link Writer#write(char[], int, int)} implementations:</p>
      *
-     * <pre>{@code
-     * @Override
+     * <pre><code>
+     * {@code @Override}
      * public int read(char[] cbuf, int off, int len) throws IOException {
      *     ensureOpen();
      *     IOUtils.checkFromIndexSize(cbuf, off, len);
@@ -480,7 +480,7 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      *     // perform read...
      * }
      *
-     * @Override
+     * {@code @Override}
      * public void write(char[] cbuf, int off, int len) throws IOException {
      *     ensureOpen();
      *     IOUtils.checkFromIndexSize(cbuf, off, len);
@@ -489,7 +489,7 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      *     }
      *     // perform write...
      * }
-     * }</pre>
+     * </code></pre>
      *
      * @param array the array against which the range is validated
      * @param off   the starting offset into the array (inclusive)
@@ -518,8 +518,8 @@ public static void checkFromIndexSize(final char[] array, final int off, final i
      *
      * <p>Typical usage in {@link Writer#write(String, int, int)} implementations:</p>
      *
-     * <pre>{@code
-     * @Override
+     * <pre><code>
+     * {@code @Override}
      * public void write(String str, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(str, off, len);
      *     if (len == 0) {
@@ -527,7 +527,7 @@ public static void checkFromIndexSize(final char[] array, final int off, final i
      *     }
      *     // perform write...
      * }
-     * }</pre>
+     * </code></pre>
      *
      * @param str the string against which the range is validated
      * @param off the starting offset into the string (inclusive)
@@ -563,14 +563,14 @@ static void checkFromIndexSize(final int off, final int len, final int arrayLeng
      *
      * <p>Typical usage in {@link Appendable#append(CharSequence, int, int)} implementations:</p>
      *
-     * <pre>{@code
-     * @Override
+     * <pre><code>
+     * {@code @Override}
      * public Appendable append(CharSequence csq, int start, int end) throws IOException {
      *     IOUtils.checkFromToIndex(csq, start, end);
      *     // perform append...
      *     return this;
      * }
-     * }</pre>
+     * </code></pre>
      *
      * @param seq       the character sequence to validate (may be {@code null}, treated as {@code "null"})
      * @param fromIndex the starting index (inclusive)

From 41c2a98b4f8d2214051cc35bacd31664cd1ce2a4 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Mon, 29 Sep 2025 11:25:02 +0200
Subject: [PATCH 08/25] fix: remove `@Override` from code snippet

There is no way to insert `@Override` in a Javadoc snippet without triggering a warning in either Java 8 or 21.
---
 src/main/java/org/apache/commons/io/IOUtils.java | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index 09c48f139d0..3f257692606 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -421,7 +421,6 @@ private static char[] charArray(final int size) {
      * <p>Typical usage in {@link InputStream#read(byte[], int, int)} and {@link OutputStream#write(byte[], int, int)} implementations:</p>
      *
      * <pre><code>
-     * {@code @Override}
      * public int read(byte[] b, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(b, off, len);
      *     if (len == 0) {
@@ -431,7 +430,6 @@ private static char[] charArray(final int size) {
      *     // perform read...
      * }
      *
-     * {@code @Override}
      * public void write(byte[] b, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(b, off, len);
      *     if (len == 0) {
@@ -470,7 +468,6 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      * <p>Typical usage in {@link Reader#read(char[], int, int)} and {@link Writer#write(char[], int, int)} implementations:</p>
      *
      * <pre><code>
-     * {@code @Override}
      * public int read(char[] cbuf, int off, int len) throws IOException {
      *     ensureOpen();
      *     IOUtils.checkFromIndexSize(cbuf, off, len);
@@ -480,7 +477,6 @@ public static void checkFromIndexSize(final byte[] array, final int off, final i
      *     // perform read...
      * }
      *
-     * {@code @Override}
      * public void write(char[] cbuf, int off, int len) throws IOException {
      *     ensureOpen();
      *     IOUtils.checkFromIndexSize(cbuf, off, len);
@@ -519,7 +515,6 @@ public static void checkFromIndexSize(final char[] array, final int off, final i
      * <p>Typical usage in {@link Writer#write(String, int, int)} implementations:</p>
      *
      * <pre><code>
-     * {@code @Override}
      * public void write(String str, int off, int len) throws IOException {
      *     IOUtils.checkFromIndexSize(str, off, len);
      *     if (len == 0) {
@@ -564,7 +559,6 @@ static void checkFromIndexSize(final int off, final int len, final int arrayLeng
      * <p>Typical usage in {@link Appendable#append(CharSequence, int, int)} implementations:</p>
      *
      * <pre><code>
-     * {@code @Override}
      * public Appendable append(CharSequence csq, int start, int end) throws IOException {
      *     IOUtils.checkFromToIndex(csq, start, end);
      *     // perform append...

From 68c1ba463d3d0d48ddf2e0ea0a06c5153d5052e1 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 08:51:01 +0200
Subject: [PATCH 09/25] fix: `ClosedReader` Javadoc and tests

---
 .../apache/commons/io/input/ClosedReader.java | 17 ++++++++----
 .../commons/io/input/ClosedReaderTest.java    | 27 ++++++++++++++-----
 2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/ClosedReader.java b/src/main/java/org/apache/commons/io/input/ClosedReader.java
index 72220c6978d..b50721c120d 100644
--- a/src/main/java/org/apache/commons/io/input/ClosedReader.java
+++ b/src/main/java/org/apache/commons/io/input/ClosedReader.java
@@ -62,12 +62,19 @@ public void close() throws IOException {
     }
 
     /**
-     * Returns -1 to indicate that the stream is closed.
+     * A no-op read method that always indicates end-of-stream.
      *
-     * @param cbuf ignored
-     * @param off ignored
-     * @param len ignored
-     * @return always -1
+     * <p>Behavior:</p>
+     * <ul>
+     *   <li>If {@code len == 0}, returns {@code 0} immediately (no characters are read).</li>
+     *   <li>Otherwise, always returns {@value IOUtils#EOF} to signal that the stream is closed or at end-of-stream.</li>
+     * </ul>
+     *
+     * @param cbuf The destination buffer.
+     * @param off  The offset at which to start storing characters.
+     * @param len  The maximum number of characters to read.
+     * @return {@code 0} if {@code len == 0}; otherwise always {@value IOUtils#EOF}.
+     * @throws IndexOutOfBoundsException If {@code off < 0}, {@code len < 0}, or {@code off + len > cbuf.length}.
      */
     @Override
     public int read(final char[] cbuf, final int off, final int len) {
diff --git a/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java b/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
index 891049f9ef5..57b87ddfb09 100644
--- a/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/ClosedReaderTest.java
@@ -18,6 +18,7 @@
 
 import static org.apache.commons.io.IOUtils.EOF;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.io.IOException;
 import java.io.Reader;
@@ -47,24 +48,38 @@ void testReadArray() throws Exception {
             assertEquals(EOF, reader.read(new char[4096]));
             assertEquals(EOF, reader.read(new char[1]));
             assertEquals(0, reader.read(new char[0]));
+            assertThrows(NullPointerException.class, () -> reader.read((char[]) null));
         }
     }
 
     @Test
     void testReadArrayIndex() throws Exception {
         try (Reader reader = new ClosedReader()) {
-            assertEquals(EOF, reader.read(CharBuffer.wrap(new char[4096])));
-            assertEquals(EOF, reader.read(CharBuffer.wrap(new char[1])));
-            assertEquals(0, reader.read(CharBuffer.wrap(new char[0])));
+            final char[] cbuf = new char[4096];
+            assertEquals(EOF, reader.read(cbuf, 0, 2048));
+            assertEquals(EOF, reader.read(cbuf, 2048, 2048));
+            assertEquals(0, reader.read(cbuf, 4096, 0));
+            assertThrows(IndexOutOfBoundsException.class, () -> reader.read(cbuf, -1, 1));
+            assertThrows(IndexOutOfBoundsException.class, () -> reader.read(cbuf, 0, 4097));
+            assertThrows(IndexOutOfBoundsException.class, () -> reader.read(cbuf, 1, -1));
+
+            assertEquals(EOF, reader.read(new char[1]));
+            assertEquals(0, reader.read(new char[0]));
+            assertThrows(NullPointerException.class, () -> reader.read(null, 0, 0));
         }
     }
 
     @Test
     void testReadCharBuffer() throws Exception {
         try (Reader reader = new ClosedReader()) {
-            assertEquals(EOF, reader.read(new char[4096]));
-            assertEquals(EOF, reader.read(new char[1]));
-            assertEquals(0, reader.read(new char[0]));
+            final CharBuffer charBuffer = CharBuffer.wrap(new char[4096]);
+            assertEquals(EOF, reader.read(charBuffer));
+            charBuffer.position(4096);
+            assertEquals(0, reader.read(charBuffer));
+
+            assertEquals(EOF, reader.read(CharBuffer.wrap(new char[1])));
+            assertEquals(0, reader.read(CharBuffer.wrap(new char[0])));
+            assertThrows(NullPointerException.class, () -> reader.read((CharBuffer) null));
         }
     }
 

From 48fe1c34398470fb139ed306c48885c91da9f857 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 09:25:54 +0200
Subject: [PATCH 10/25] fix: revert `BrokenReader` and add tests

The tests are improved to ensure that the given exception is thrown **before** parameter validation.
---
 .../apache/commons/io/input/BrokenReader.java | 30 ++++++++++++++---
 .../commons/io/input/BrokenReaderTest.java    | 32 ++++++++++++++++---
 2 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/BrokenReader.java b/src/main/java/org/apache/commons/io/input/BrokenReader.java
index 61e9bff47ba..f5d5b3b4e13 100644
--- a/src/main/java/org/apache/commons/io/input/BrokenReader.java
+++ b/src/main/java/org/apache/commons/io/input/BrokenReader.java
@@ -18,9 +18,9 @@
 
 import java.io.IOException;
 import java.io.Reader;
+import java.nio.CharBuffer;
 import java.util.function.Supplier;
 
-import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.Erase;
 
 /**
@@ -115,10 +115,30 @@ public void mark(final int readAheadLimit) throws IOException {
      */
     @Override
     public int read(final char[] cbuf, final int off, final int len) throws IOException {
-        IOUtils.checkFromIndexSize(cbuf, off, len);
-        if (len == 0) {
-            return 0;
-        }
+        throw rethrow();
+    }
+
+    /**
+     * Throws the configured exception.
+     *
+     * @param target ignored.
+     * @return nothing.
+     * @throws IOException always throws the exception configured in a constructor.
+     */
+    @Override
+    public int read(CharBuffer target) throws IOException {
+        throw rethrow();
+    }
+
+    /**
+     * Throws the configured exception.
+     *
+     * @param cbuf ignored.
+     * @return nothing.
+     * @throws IOException always throws the exception configured in a constructor.
+     */
+    @Override
+    public int read(char[] cbuf) throws IOException {
         throw rethrow();
     }
 
diff --git a/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java b/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
index aca91077e6b..02c535a9ec3 100644
--- a/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
@@ -22,6 +22,7 @@
 
 import java.io.IOException;
 import java.io.Reader;
+import java.nio.CharBuffer;
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -45,7 +46,7 @@ void testClose(final Class<Exception> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.close()));
+        assertEquals(exception, assertThrows(clazz, brokenReader::close));
     }
 
     @Test
@@ -68,7 +69,7 @@ void testRead(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read()));
+        assertEquals(exception, assertThrows(clazz, brokenReader::read));
     }
 
     @ParameterizedTest
@@ -78,6 +79,8 @@ void testReadCharArray(final Class<Throwable> clazz) throws Exception {
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
         assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(new char[1])));
+        // Also throws the exception before checking arguments
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read((char[]) null)));
     }
 
     @ParameterizedTest
@@ -86,7 +89,26 @@ void testReadCharArrayIndexed(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(new char[1], 0, 1)));
+        final char[] cbuf = new char[1];
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(cbuf, 0, 1)));
+        // Also throws the exception before checking arguments
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(cbuf, -1, 1)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(cbuf, 0, -1)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(cbuf, 1, 1)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(null, 0, 0)));
+
+    }
+
+    @ParameterizedTest
+    @MethodSource("org.apache.commons.io.BrokenTestFactories#parameters")
+    void testReadCharBuffer(final Class<Throwable> clazz) throws Exception {
+        final Throwable exception = clazz.newInstance();
+        @SuppressWarnings("resource")
+        final BrokenReader brokenReader = createBrokenReader(exception);
+        final CharBuffer charBuffer = CharBuffer.allocate(1);
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(charBuffer)));
+        // Also throws the exception before checking arguments
+        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read((CharBuffer) null)));
     }
 
     @ParameterizedTest
@@ -95,7 +117,7 @@ void testReady(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.ready()));
+        assertEquals(exception, assertThrows(clazz, brokenReader::ready));
     }
 
     @ParameterizedTest
@@ -104,7 +126,7 @@ void testReset(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.reset()));
+        assertEquals(exception, assertThrows(clazz, brokenReader::reset));
     }
 
     @ParameterizedTest

From bbde62705159668acddaaab29163346e06d05119 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 10:05:32 +0200
Subject: [PATCH 11/25] fix: remove `BrokenReader.read(char[]/CharBuffer)`
 overrides

---
 .../apache/commons/io/input/BrokenReader.java | 24 -------------------
 .../commons/io/input/BrokenReaderTest.java    |  4 ----
 2 files changed, 28 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/BrokenReader.java b/src/main/java/org/apache/commons/io/input/BrokenReader.java
index f5d5b3b4e13..2467228b9a9 100644
--- a/src/main/java/org/apache/commons/io/input/BrokenReader.java
+++ b/src/main/java/org/apache/commons/io/input/BrokenReader.java
@@ -118,30 +118,6 @@ public int read(final char[] cbuf, final int off, final int len) throws IOExcept
         throw rethrow();
     }
 
-    /**
-     * Throws the configured exception.
-     *
-     * @param target ignored.
-     * @return nothing.
-     * @throws IOException always throws the exception configured in a constructor.
-     */
-    @Override
-    public int read(CharBuffer target) throws IOException {
-        throw rethrow();
-    }
-
-    /**
-     * Throws the configured exception.
-     *
-     * @param cbuf ignored.
-     * @return nothing.
-     * @throws IOException always throws the exception configured in a constructor.
-     */
-    @Override
-    public int read(char[] cbuf) throws IOException {
-        throw rethrow();
-    }
-
     /**
      * Throws the configured exception.
      *
diff --git a/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java b/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
index 02c535a9ec3..a47687abf3d 100644
--- a/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
+++ b/src/test/java/org/apache/commons/io/input/BrokenReaderTest.java
@@ -79,8 +79,6 @@ void testReadCharArray(final Class<Throwable> clazz) throws Exception {
         @SuppressWarnings("resource")
         final BrokenReader brokenReader = createBrokenReader(exception);
         assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(new char[1])));
-        // Also throws the exception before checking arguments
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read((char[]) null)));
     }
 
     @ParameterizedTest
@@ -107,8 +105,6 @@ void testReadCharBuffer(final Class<Throwable> clazz) throws Exception {
         final BrokenReader brokenReader = createBrokenReader(exception);
         final CharBuffer charBuffer = CharBuffer.allocate(1);
         assertEquals(exception, assertThrows(clazz, () -> brokenReader.read(charBuffer)));
-        // Also throws the exception before checking arguments
-        assertEquals(exception, assertThrows(clazz, () -> brokenReader.read((CharBuffer) null)));
     }
 
     @ParameterizedTest

From de2d1e376421622ea3f700e6c59ff90a8e2c143d Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 10:13:51 +0200
Subject: [PATCH 12/25] fix: revert `BrokenWriter`

Revert `BrokenWriter` and add test cases to ensure the exception is thrown **before** parameter validation.
---
 .../org/apache/commons/io/output/BrokenWriter.java |  2 --
 .../apache/commons/io/output/BrokenWriterTest.java | 14 +++++++++++---
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/BrokenWriter.java b/src/main/java/org/apache/commons/io/output/BrokenWriter.java
index 1feac6bb84a..7fe244d2392 100644
--- a/src/main/java/org/apache/commons/io/output/BrokenWriter.java
+++ b/src/main/java/org/apache/commons/io/output/BrokenWriter.java
@@ -20,7 +20,6 @@
 import java.io.Writer;
 import java.util.function.Supplier;
 
-import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.Erase;
 
 /**
@@ -122,7 +121,6 @@ private RuntimeException rethrow() {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
-        IOUtils.checkFromIndexSize(cbuf, off, len);
         throw rethrow();
     }
 
diff --git a/src/test/java/org/apache/commons/io/output/BrokenWriterTest.java b/src/test/java/org/apache/commons/io/output/BrokenWriterTest.java
index f8db50a6729..dffeb7907ae 100644
--- a/src/test/java/org/apache/commons/io/output/BrokenWriterTest.java
+++ b/src/test/java/org/apache/commons/io/output/BrokenWriterTest.java
@@ -55,6 +55,7 @@ void testAppendCharSequence(final Class<Throwable> clazz) throws Exception {
         @SuppressWarnings("resource")
         final BrokenWriter brokenWriter = createBrokenWriter(exception);
         assertEquals(exception, assertThrows(clazz, () -> brokenWriter.append("01")));
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.append(null)));
     }
 
     @ParameterizedTest
@@ -64,6 +65,7 @@ void testAppendCharSequenceIndexed(final Class<Throwable> clazz) throws Exceptio
         @SuppressWarnings("resource")
         final BrokenWriter brokenWriter = createBrokenWriter(exception);
         assertEquals(exception, assertThrows(clazz, () -> brokenWriter.append("01", 0, 1)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.append(null, 0, 4)));
     }
 
     @ParameterizedTest
@@ -72,7 +74,7 @@ void testClose(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenWriter brokenWriter = createBrokenWriter(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.close()));
+        assertEquals(exception, assertThrows(clazz, brokenWriter::close));
     }
 
     @ParameterizedTest
@@ -81,7 +83,7 @@ void testFlush(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenWriter brokenWriter = createBrokenWriter(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.flush()));
+        assertEquals(exception, assertThrows(clazz, brokenWriter::flush));
     }
 
     @Test
@@ -119,7 +121,13 @@ void testWriteCharArrayIndexed(final Class<Throwable> clazz) throws Exception {
         final Throwable exception = clazz.newInstance();
         @SuppressWarnings("resource")
         final BrokenWriter brokenWriter = createBrokenWriter(exception);
-        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write(new char[1], 0, 1)));
+        final char[] cbuf = new char[1];
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write(cbuf, 0, 1)));
+        // Verify that the exception is thrown before checking the parameters.
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write(cbuf, -1, 0)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write(cbuf, 0, -1)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write(cbuf, 0, 2)));
+        assertEquals(exception, assertThrows(clazz, () -> brokenWriter.write((char[]) null, 0, 0)));
     }
 
     @ParameterizedTest

From b0bea24988abd922d640ffacc20abe3b5201cc42 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 10:14:59 +0200
Subject: [PATCH 13/25] fix: Checkstyle failures

---
 src/main/java/org/apache/commons/io/input/BrokenReader.java | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/main/java/org/apache/commons/io/input/BrokenReader.java b/src/main/java/org/apache/commons/io/input/BrokenReader.java
index 2467228b9a9..8fb510569cf 100644
--- a/src/main/java/org/apache/commons/io/input/BrokenReader.java
+++ b/src/main/java/org/apache/commons/io/input/BrokenReader.java
@@ -18,7 +18,6 @@
 
 import java.io.IOException;
 import java.io.Reader;
-import java.nio.CharBuffer;
 import java.util.function.Supplier;
 
 import org.apache.commons.io.function.Erase;

From 06cb03b158c105427f79c1c39b7a50a5bb57ba8d Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 10:33:13 +0200
Subject: [PATCH 14/25] fix: revert `ClosedWriter` and add tests

---
 .../java/org/apache/commons/io/output/ClosedWriter.java   | 6 ++----
 .../org/apache/commons/io/output/ClosedWriterTest.java    | 8 +++++++-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/ClosedWriter.java b/src/main/java/org/apache/commons/io/output/ClosedWriter.java
index bc1add898ad..c4e1d93b93c 100644
--- a/src/main/java/org/apache/commons/io/output/ClosedWriter.java
+++ b/src/main/java/org/apache/commons/io/output/ClosedWriter.java
@@ -19,8 +19,7 @@
 
 import java.io.IOException;
 import java.io.Writer;
-
-import org.apache.commons.io.IOUtils;
+import java.util.Arrays;
 
 /**
  * Throws an IOException on all attempts to write with {@link #close()} implemented as a noop.
@@ -79,7 +78,6 @@ public void flush() throws IOException {
      */
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
-        IOUtils.checkFromIndexSize(cbuf, off, len);
-        throw new IOException("write(" + new String(cbuf) + ", " + off + ", " + len + ") failed: stream is closed");
+        throw new IOException(String.format("write(%s, %d, %d) failed: stream is closed", Arrays.toString(cbuf), off, len));
     }
 }
diff --git a/src/test/java/org/apache/commons/io/output/ClosedWriterTest.java b/src/test/java/org/apache/commons/io/output/ClosedWriterTest.java
index 4f57957a885..b9758729f1b 100644
--- a/src/test/java/org/apache/commons/io/output/ClosedWriterTest.java
+++ b/src/test/java/org/apache/commons/io/output/ClosedWriterTest.java
@@ -43,7 +43,13 @@ void testFlush() throws IOException {
     @Test
     void testWrite() throws IOException {
         try (ClosedWriter cw = new ClosedWriter()) {
-            assertThrows(IOException.class, () -> cw.write(new char[0], 0, 0));
+            final char[] cbuf = new char[1];
+            assertThrows(IOException.class, () -> cw.write(new char[0], 0, 1));
+            // In writers, testing for closed always comes before argument validation
+            assertThrows(IOException.class, () -> cw.write(cbuf, -1, 0));
+            assertThrows(IOException.class, () -> cw.write(cbuf, 0, -1));
+            assertThrows(IOException.class, () -> cw.write(cbuf, 0, 2));
+            assertThrows(IOException.class, () -> cw.write((char[]) null, 0, 0));
         }
     }
 

From 3678d1e22600febb067c606171ab77ff26c77241 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 10:50:19 +0200
Subject: [PATCH 15/25] fix: revert `FilterCollectionWriter` changes

---
 .../org/apache/commons/io/output/FilterCollectionWriter.java   | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java b/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
index 1a13d90eff3..d78f049e635 100644
--- a/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
+++ b/src/main/java/org/apache/commons/io/output/FilterCollectionWriter.java
@@ -28,7 +28,6 @@
 
 import org.apache.commons.io.IOExceptionList;
 import org.apache.commons.io.IOIndexedException;
-import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.function.IOConsumer;
 
 /**
@@ -129,7 +128,6 @@ public void write(final char[] cbuf) throws IOException {
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
-        IOUtils.checkFromIndexSize(cbuf, off, len);
         forAllWriters(w -> w.write(cbuf, off, len));
     }
 
@@ -161,7 +159,6 @@ public void write(final String str) throws IOException {
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final String str, final int off, final int len) throws IOException {
-        IOUtils.checkFromIndexSize(str, off, len);
         forAllWriters(w -> w.write(str, off, len));
     }
 

From d00d5effe0da276f7c0d0caa1b1cef77f6c2103d Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 11:03:24 +0200
Subject: [PATCH 16/25] fix: fix `NullAppendable` Javadoc

---
 .../apache/commons/io/output/NullAppendable.java  | 15 +++++++++++++++
 .../commons/io/output/NullAppendableTest.java     | 10 ++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/NullAppendable.java b/src/main/java/org/apache/commons/io/output/NullAppendable.java
index fee5dace602..7adbc2d3749 100644
--- a/src/main/java/org/apache/commons/io/output/NullAppendable.java
+++ b/src/main/java/org/apache/commons/io/output/NullAppendable.java
@@ -51,6 +51,21 @@ public Appendable append(final CharSequence csq) throws IOException {
         return this;
     }
 
+    /**
+     * Appends a subsequence of the specified character sequence to this Appendable.
+     *
+     * @param csq   The character sequence from which a subsequence will be
+     *              appended.
+     *              If {@code csq} is {@code null}, it is treated as if it were
+     *              {@code "null"}.
+     * @param start The index of the first character in the subsequence.
+     * @param end   The index of the character following the last character in the
+     *              subsequence.
+     * @return {@code this} instance.
+     * @throws IndexOutOfBoundsException if {@code start} or {@code end} are negative, {@code end} is
+     *                                   greater than {@code csq.length()}, or {@code start} is greater
+     *                                   than {@code end}.
+     */
     @Override
     public Appendable append(final CharSequence csq, final int start, final int end) throws IOException {
         IOUtils.checkFromToIndex(csq, start, end);
diff --git a/src/test/java/org/apache/commons/io/output/NullAppendableTest.java b/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
index 09b1d1bf2ba..aa5ef7137ed 100644
--- a/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
+++ b/src/test/java/org/apache/commons/io/output/NullAppendableTest.java
@@ -34,10 +34,12 @@ void testNull() throws IOException {
         appendable.append("A");
         appendable.append("A", 0, 1);
         appendable.append(null, 0, 1);
-        // `null` is converted to "null"
-        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, -1, 0));
-        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, 1, 0));
-        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(null, 0, 5));
+        // Check argument validation
+        final CharSequence csq = "ABCDE";
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(csq, -1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(csq, 0, -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(csq, 1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> appendable.append(csq, 0, 6));
     }
 
 }

From 1e558f5e05cb2c67fc3a4f7404a73ddae02c6a81 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 11:09:22 +0200
Subject: [PATCH 17/25] fix: fix `NullOutputStream` Javadoc and enhance tests

---
 .../apache/commons/io/output/NullOutputStream.java  | 13 +++++++++----
 .../commons/io/output/NullOutputStreamTest.java     | 11 ++++++++++-
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/NullOutputStream.java b/src/main/java/org/apache/commons/io/output/NullOutputStream.java
index 682d0f8e768..0334a4ea4b8 100644
--- a/src/main/java/org/apache/commons/io/output/NullOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/NullOutputStream.java
@@ -69,11 +69,16 @@ public void write(final byte[] b) throws IOException {
     }
 
     /**
-     * Does nothing.
+     * No-op operation.
      *
-     * @param b This method ignores this parameter.
-     * @param off This method ignores this parameter.
-     * @param len This method ignores this parameter.
+     * <p>Validates the arguments but does not write the data.</p>
+     *
+     * @param b   The byte array to write from, not {@code null}.
+     * @param off The offset to start at.
+     * @param len The number of bytes to write.
+     * @throws NullPointerException      If {@code b} is {@code null}.
+     * @throws IndexOutOfBoundsException If {@code off} or {@code len} are negative, {@code off + len} is greater than
+     *                                   {@code b.length}.
      */
     @Override
     public void write(final byte[] b, final int off, final int len) {
diff --git a/src/test/java/org/apache/commons/io/output/NullOutputStreamTest.java b/src/test/java/org/apache/commons/io/output/NullOutputStreamTest.java
index bdecc0e0a68..097566fc6e2 100644
--- a/src/test/java/org/apache/commons/io/output/NullOutputStreamTest.java
+++ b/src/test/java/org/apache/commons/io/output/NullOutputStreamTest.java
@@ -16,6 +16,8 @@
  */
 package org.apache.commons.io.output;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import java.io.IOException;
 
 import org.junit.jupiter.api.Test;
@@ -34,11 +36,18 @@ private void process(final NullOutputStream nos) throws IOException {
         nos.close();
         nos.write("allowed".getBytes());
         nos.write(255);
+        // Test arguments validation
+        final byte[] b = new byte[1];
+        assertThrows(IndexOutOfBoundsException.class, () -> nos.write(b, -1, 0));
+        assertThrows(IndexOutOfBoundsException.class, () -> nos.write(b, 0, -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> nos.write(b, 0, 2));
+        assertThrows(NullPointerException.class, () -> nos.write(null, 0, 0));
     }
 
     @Test
+    @SuppressWarnings("deprecation")
     void testNewInstance() throws IOException {
-        try (NullOutputStream nos = NullOutputStream.INSTANCE) {
+        try (NullOutputStream nos = new NullOutputStream()) {
             process(nos);
         }
     }

From 6585383d23a7cc02acfb977125b16e00965d5458 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 11:37:35 +0200
Subject: [PATCH 18/25] fix: fix `NullWriter` Javadoc and enhance tests

---
 .../commons/io/output/NullAppendable.java     |  4 +-
 .../apache/commons/io/output/NullWriter.java  | 47 +++++----
 .../commons/io/output/NullWriterTest.java     | 96 +++++++++++++++++--
 3 files changed, 121 insertions(+), 26 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/NullAppendable.java b/src/main/java/org/apache/commons/io/output/NullAppendable.java
index 7adbc2d3749..c5ea2cfcbeb 100644
--- a/src/main/java/org/apache/commons/io/output/NullAppendable.java
+++ b/src/main/java/org/apache/commons/io/output/NullAppendable.java
@@ -52,7 +52,7 @@ public Appendable append(final CharSequence csq) throws IOException {
     }
 
     /**
-     * Appends a subsequence of the specified character sequence to this Appendable.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
      * @param csq   The character sequence from which a subsequence will be
      *              appended.
@@ -62,7 +62,7 @@ public Appendable append(final CharSequence csq) throws IOException {
      * @param end   The index of the character following the last character in the
      *              subsequence.
      * @return {@code this} instance.
-     * @throws IndexOutOfBoundsException if {@code start} or {@code end} are negative, {@code end} is
+     * @throws IndexOutOfBoundsException If {@code start} or {@code end} are negative, {@code end} is
      *                                   greater than {@code csq.length()}, or {@code start} is greater
      *                                   than {@code end}.
      */
diff --git a/src/main/java/org/apache/commons/io/output/NullWriter.java b/src/main/java/org/apache/commons/io/output/NullWriter.java
index 9741b819766..0ef9a09cdbf 100644
--- a/src/main/java/org/apache/commons/io/output/NullWriter.java
+++ b/src/main/java/org/apache/commons/io/output/NullWriter.java
@@ -79,12 +79,19 @@ public Writer append(final CharSequence csq) {
     }
 
     /**
-     * Does nothing, like writing to {@code /dev/null}.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
-     * @param csq The character sequence to write.
-     * @param start The index of the first character to write.
-     * @param end  The index of the first character to write (exclusive).
-     * @return this writer.
+     * @param csq   The character sequence from which a subsequence will be
+     *              appended.
+     *              If {@code csq} is {@code null}, it is treated as if it were
+     *              {@code "null"}.
+     * @param start The index of the first character in the subsequence.
+     * @param end   The index of the character following the last character in the
+     *              subsequence.
+     * @return {@code this} instance.
+     * @throws IndexOutOfBoundsException If {@code start} or {@code end} are negative, {@code end} is
+     *                                   greater than {@code csq.length()}, or {@code start} is greater
+     *                                   than {@code end}.
      * @since 2.0
      */
     @Override
@@ -106,9 +113,10 @@ public void flush() {
     }
 
     /**
-     * Does nothing, like writing to {@code /dev/null}.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
-     * @param chr The characters to write
+     * @param chr The characters to write, not {@code null}.
+     * @throws NullPointerException if {@code chr} is {@code null}.
      */
     @Override
     public void write(final char[] chr) {
@@ -117,15 +125,17 @@ public void write(final char[] chr) {
     }
 
     /**
-     * Does nothing, like writing to {@code /dev/null}.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
-     * @param chr The characters to write.
-     * @param st The start offset.
-     * @param end The number of characters to write.
+     * @param cbuf The characters to write, not {@code null}.
+     * @param off  The start offset.
+     * @param len  The number of characters to write.
+     * @throws NullPointerException      if {@code chr} is {@code null}.
+     * @throws IndexOutOfBoundsException If ({@code off} or {@code len} are negative, or {@code off + len} is greater than {@code cbuf.length}.
      */
     @Override
-    public void write(final char[] chr, final int st, final int end) {
-        IOUtils.checkFromIndexSize(chr, st, end);
+    public void write(final char[] cbuf, final int off, final int len) {
+        IOUtils.checkFromIndexSize(cbuf, off, len);
         //to /dev/null
     }
 
@@ -140,9 +150,10 @@ public void write(final int b) {
     }
 
     /**
-     * Does nothing, like writing to {@code /dev/null}.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
-     * @param str The string to write.
+     * @param str The string to write, not {@code null}.
+     * @throws NullPointerException if {@code str} is {@code null}.
      */
     @Override
     public void write(final String str) {
@@ -151,11 +162,13 @@ public void write(final String str) {
     }
 
     /**
-     * Does nothing, like writing to {@code /dev/null}.
+     * Does nothing except argument validation, like writing to {@code /dev/null}.
      *
-     * @param str The string to write.
+     * @param str The string to write, not {@code null}.
      * @param off The start offset.
      * @param len The number of characters to write.
+     * @throws NullPointerException      If {@code str} is {@code null}.
+     * @throws IndexOutOfBoundsException If ({@code off} or {@code len} are negative, or {@code off + len} is greater than {@code str.length()}.
      */
     @Override
     public void write(final String str, final int off, final int len) {
diff --git a/src/test/java/org/apache/commons/io/output/NullWriterTest.java b/src/test/java/org/apache/commons/io/output/NullWriterTest.java
index f1b603a3776..424d076ee21 100644
--- a/src/test/java/org/apache/commons/io/output/NullWriterTest.java
+++ b/src/test/java/org/apache/commons/io/output/NullWriterTest.java
@@ -16,6 +16,9 @@
  */
 package org.apache.commons.io.output;
 
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import org.junit.jupiter.api.Test;
 
 /**
@@ -24,17 +27,96 @@
  */
 class NullWriterTest {
 
+    private static final String TEST_STRING = "ABC";
+    private static final char[] TEST_CHARS = TEST_STRING.toCharArray();
+
+    @Test
+    void testAppendChar() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            assertSame(writer, writer.append('X'));
+        }
+    }
+
+    @Test
+    void testAppendCharSequence() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            assertSame(writer, writer.append(TEST_STRING));
+            assertSame(writer, writer.append(null));
+        }
+    }
+
     @Test
-    void testNull() {
-        final char[] chars = { 'A', 'B', 'C' };
+    void testAppendCharSequenceWithRange() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            assertSame(writer, writer.append(TEST_STRING, 1, 2));
+            assertSame(writer, writer.append(null, 0, 4));
+            // Test argument validation
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.append(TEST_STRING, -1, 2));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.append(TEST_STRING, 1, 5));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.append(TEST_STRING, 2, 1));
+        }
+    }
+
+    @Test
+    void testCloseNoOp() {
+        final NullWriter writer = NullWriter.INSTANCE;
+        writer.close();
+        writer.write(TEST_CHARS);
+    }
+
+    @Test
+    void testFlush() {
         try (NullWriter writer = NullWriter.INSTANCE) {
-            writer.write(1);
-            writer.write(chars);
-            writer.write(chars, 1, 1);
-            writer.write("some string");
-            writer.write("some string", 2, 2);
             writer.flush();
         }
     }
 
+    @Test
+    void testWriteCharArray() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            writer.write(TEST_CHARS);
+            // Test argument validation
+            assertThrows(NullPointerException.class, () -> writer.write((char[]) null));
+        }
+    }
+
+    @Test
+    void testWriteCharArrayWithOffset() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            writer.write(TEST_CHARS, 1, 2);
+            // Test argument validation
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_CHARS, -1, 0));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_CHARS, 0, -1));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_CHARS, 0, 4));
+            assertThrows(NullPointerException.class, () -> writer.write((char[]) null, 0, 0));
+        }
+    }
+
+    @Test
+    void testWriteInt() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            writer.write(42);
+        }
+    }
+
+    @Test
+    void testWriteString() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            writer.write(TEST_STRING);
+            // Test argument validation
+            assertThrows(NullPointerException.class, () -> writer.write((String) null));
+        }
+    }
+
+    @Test
+    void testWriteStringWithOffset() {
+        try (NullWriter writer = NullWriter.INSTANCE) {
+            writer.write(TEST_STRING, 1, 1);
+            // Test argument validation
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_STRING, -1, 0));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_STRING, 0, -1));
+            assertThrows(IndexOutOfBoundsException.class, () -> writer.write(TEST_STRING, 0, 4));
+            assertThrows(NullPointerException.class, () -> writer.write((String) null, 0, 0));
+        }
+    }
 }

From 14a250629ba13693c802a5a47592b1c634e1fb2e Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:19:11 +0200
Subject: [PATCH 19/25] fix: `NullInputStream` Javadoc

---
 .../org/apache/commons/io/input/NullInputStream.java     | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/NullInputStream.java b/src/main/java/org/apache/commons/io/input/NullInputStream.java
index 32b1206ff2f..5fa9b817b5c 100644
--- a/src/main/java/org/apache/commons/io/input/NullInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/NullInputStream.java
@@ -243,9 +243,9 @@ protected int processByte() {
      * This implementation leaves the byte array unchanged.
      * </p>
      *
-     * @param bytes  The byte array
-     * @param offset The offset to start at.
-     * @param length The number of bytes.
+     * @param bytes  The byte array, never {@code null}.
+     * @param offset The offset to start at, always non-negative.
+     * @param length The number of bytes to process, always non-negative and at most {@code bytes.length - offset}.
      */
     protected void processBytes(final byte[] bytes, final int offset, final int length) {
         // do nothing - overridable by subclass
@@ -274,6 +274,7 @@ public int read() throws IOException {
      *
      * @param bytes The byte array to read into
      * @return The number of bytes read or {@code -1} if the end of file has been reached and {@code throwEofException} is set to {@code false}.
+     * @throws NullPointerException if the byte array is {@code null}.
      * @throws EOFException if the end of file is reached and {@code throwEofException} is set to {@code true}.
      * @throws IOException  if trying to read past the end of file.
      */
@@ -289,6 +290,8 @@ public int read(final byte[] bytes) throws IOException {
      * @param offset The offset to start reading bytes into.
      * @param length The number of bytes to read.
      * @return The number of bytes read or {@code -1} if the end of file has been reached and {@code throwEofException} is set to {@code false}.
+     * @throws NullPointerException if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code offset} or {@code length} are negative, or if {@code offset + length} is greater than {@code bytes.length}.
      * @throws EOFException if the end of file is reached and {@code throwEofException} is set to {@code true}.
      * @throws IOException  if trying to read past the end of file.
      */

From 1632fb2edcd4dd3f425b0e84e1111f0cfa251fe9 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:22:42 +0200
Subject: [PATCH 20/25] fix: `ClosedOutputStream` Javadoc

---
 .../org/apache/commons/io/output/ClosedOutputStream.java  | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java b/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
index faa342f40f6..c7216ce6f90 100644
--- a/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ClosedOutputStream.java
@@ -68,9 +68,11 @@ public void flush() throws IOException {
     /**
      * Throws an {@link IOException} to indicate that the stream is closed.
      *
-     * @param b   ignored.
-     * @param off ignored.
-     * @param len ignored.
+     * @param b   Byte array, never {@code null}.
+     * @param off The start offset in the byte array.
+     * @param len The number of bytes to write.
+     * @throws NullPointerException if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code b.length}.
      * @throws IOException always thrown.
      */
     @Override

From 94760281b40b4a442c7d784713525e94bb0ed694 Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:26:12 +0200
Subject: [PATCH 21/25] fix: `StringBuilderWriter` behavior and Javadoc

---
 .../org/apache/commons/io/output/StringBuilderWriter.java  | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java b/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
index 836e8bc3753..bdb757cf684 100644
--- a/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
+++ b/src/main/java/org/apache/commons/io/output/StringBuilderWriter.java
@@ -148,11 +148,14 @@ public String toString() {
      * @param value The value to write.
      * @param offset The index of the first character.
      * @param length The number of characters to write.
+     * @throws IndexOutOfBoundsException if {@code offset} or {@code length} are negative, or if {@code offset + length} is greater than {@code value.length}.
      */
     @Override
     public void write(final char[] value, final int offset, final int length) {
-        IOUtils.checkFromIndexSize(value, offset, length);
-        builder.append(value, offset, length);
+        if (value != null) {
+            IOUtils.checkFromIndexSize(value, offset, length);
+            builder.append(value, offset, length);
+        }
     }
 
     /**

From b80971821c227b09de4e2aec5a2adcee7b4b4a3b Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:27:41 +0200
Subject: [PATCH 22/25] fix: restore `NullWriter` comment

---
 src/main/java/org/apache/commons/io/output/NullWriter.java | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/main/java/org/apache/commons/io/output/NullWriter.java b/src/main/java/org/apache/commons/io/output/NullWriter.java
index 0ef9a09cdbf..635ffb044a6 100644
--- a/src/main/java/org/apache/commons/io/output/NullWriter.java
+++ b/src/main/java/org/apache/commons/io/output/NullWriter.java
@@ -97,6 +97,7 @@ public Writer append(final CharSequence csq) {
     @Override
     public Writer append(final CharSequence csq, final int start, final int end) {
         IOUtils.checkFromToIndex(csq, start, end);
+        //to /dev/null
         return this;
     }
 

From a70be15bbb8c493a95144542f5a8fd8788e5b8cd Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:32:30 +0200
Subject: [PATCH 23/25] fix: `checkFromToIndex` logical or

---
 src/main/java/org/apache/commons/io/IOUtils.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main/java/org/apache/commons/io/IOUtils.java b/src/main/java/org/apache/commons/io/IOUtils.java
index 3f257692606..a882d4d87cb 100644
--- a/src/main/java/org/apache/commons/io/IOUtils.java
+++ b/src/main/java/org/apache/commons/io/IOUtils.java
@@ -578,7 +578,7 @@ public static void checkFromToIndex(final CharSequence seq, final int fromIndex,
     }
 
     static void checkFromToIndex(final int fromIndex, final int toIndex, final int length) {
-        if (fromIndex < 0 | toIndex < fromIndex | length < toIndex) {
+        if (fromIndex < 0 || toIndex < fromIndex || length < toIndex) {
             throw new IndexOutOfBoundsException(String.format("Range [%s, %s) out of bounds for length %s", fromIndex, toIndex, length));
         }
     }

From 8d520f72c3698440e2275b860a991a41757ad2fb Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:50:40 +0200
Subject: [PATCH 24/25] fix: document `IndexOutOfBoundsException`

---
 .../java/org/apache/commons/io/input/BOMInputStream.java  | 8 +++++++-
 .../java/org/apache/commons/io/input/BoundedReader.java   | 2 ++
 .../org/apache/commons/io/input/CharSequenceReader.java   | 5 +++--
 src/main/java/org/apache/commons/io/input/NullReader.java | 2 ++
 .../org/apache/commons/io/input/ReaderInputStream.java    | 5 ++++-
 .../java/org/apache/commons/io/input/SequenceReader.java  | 5 -----
 .../org/apache/commons/io/output/AppendableWriter.java    | 6 ++++++
 .../org/apache/commons/io/output/ChunkedOutputStream.java | 3 +++
 .../java/org/apache/commons/io/output/ChunkedWriter.java  | 3 +++
 .../org/apache/commons/io/output/WriterOutputStream.java  | 3 +++
 .../org/apache/commons/io/output/XmlStreamWriter.java     | 3 +++
 11 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/BOMInputStream.java b/src/main/java/org/apache/commons/io/input/BOMInputStream.java
index 4cb347f1dc5..acfe8d9ddbb 100644
--- a/src/main/java/org/apache/commons/io/input/BOMInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/BOMInputStream.java
@@ -419,8 +419,10 @@ public int read() throws IOException {
      * Invokes the delegate's {@code read(byte[])} method, detecting and optionally skipping BOM.
      *
      * @param buf
-     *            the buffer to read the bytes into
+     *            the buffer to read the bytes into, never {@code null}
      * @return the number of bytes read (excluding BOM) or -1 if the end of stream
+     * @throws NullPointerException
+     *             if the buffer is {@code null}
      * @throws IOException
      *             if an I/O error occurs
      */
@@ -439,6 +441,10 @@ public int read(final byte[] buf) throws IOException {
      * @param len
      *            The number of bytes to read (excluding BOM)
      * @return the number of bytes read or -1 if the end of stream
+     * @throws NullPointerException
+     *             if the buffer is {@code null}
+     * @throws IndexOutOfBoundsException
+     *             if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code buf.length}
      * @throws IOException
      *             if an I/O error occurs
      */
diff --git a/src/main/java/org/apache/commons/io/input/BoundedReader.java b/src/main/java/org/apache/commons/io/input/BoundedReader.java
index c64759045f2..5c1c255c0fe 100644
--- a/src/main/java/org/apache/commons/io/input/BoundedReader.java
+++ b/src/main/java/org/apache/commons/io/input/BoundedReader.java
@@ -118,6 +118,8 @@ public int read() throws IOException {
      * @param off  The offset
      * @param len  The number of chars to read
      * @return the number of chars read
+     * @throws NullPointerException if the buffer is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code cbuf.length}.
      * @throws IOException If an I/O error occurs while calling the underlying reader's read method
      * @see Reader#read(char[], int, int)
      */
diff --git a/src/main/java/org/apache/commons/io/input/CharSequenceReader.java b/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
index bc3defe7ddc..bb2be3692c9 100644
--- a/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
+++ b/src/main/java/org/apache/commons/io/input/CharSequenceReader.java
@@ -205,8 +205,9 @@ public int read() {
      * @param array The array to store the characters in
      * @param offset The starting position in the array to store
      * @param length The maximum number of characters to read
-     * @return The number of characters read or -1 if there are
-     * no more
+     * @return The number of characters read or -1 if there are no more
+     * @throws NullPointerException if the array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code offset} or {@code length} are negative, or if {@code offset + length} is greater than {@code array.length}.
      */
     @Override
     public int read(final char[] array, final int offset, final int length) {
diff --git a/src/main/java/org/apache/commons/io/input/NullReader.java b/src/main/java/org/apache/commons/io/input/NullReader.java
index 2b7fdb47175..28f3d37eb21 100644
--- a/src/main/java/org/apache/commons/io/input/NullReader.java
+++ b/src/main/java/org/apache/commons/io/input/NullReader.java
@@ -272,6 +272,8 @@ public int read(final char[] chars) throws IOException {
      * @return The number of characters read or {@code -1}
      * if the end of file has been reached and
      * {@code throwEofException} is set to {@code false}.
+     * @throws NullPointerException if the array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code offset} or {@code length} are negative, or if {@code offset + length} is greater than {@code chars.length}.
      * @throws EOFException if the end of file is reached and
      * {@code throwEofException} is set to {@code true}.
      * @throws IOException if trying to read past the end of file.
diff --git a/src/main/java/org/apache/commons/io/input/ReaderInputStream.java b/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
index b2b6a82befb..4d22d28f891 100644
--- a/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/ReaderInputStream.java
@@ -435,8 +435,9 @@ public int read() throws IOException {
     /**
      * Reads the specified number of bytes into an array.
      *
-     * @param b the byte array to read into
+     * @param b the byte array to read into, must not be {@code null}
      * @return the number of bytes read or {@code -1} if the end of the stream has been reached
+     * @throws NullPointerException if the byte array is {@code null}.
      * @throws IOException if an I/O error occurs.
      */
     @Override
@@ -451,6 +452,8 @@ public int read(final byte[] b) throws IOException {
      * @param off   the offset to start reading bytes into
      * @param len   the number of bytes to read
      * @return the number of bytes read or {@code -1} if the end of the stream has been reached
+     * @throws NullPointerException      if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code array.length}.
      * @throws IOException if an I/O error occurs.
      */
     @Override
diff --git a/src/main/java/org/apache/commons/io/input/SequenceReader.java b/src/main/java/org/apache/commons/io/input/SequenceReader.java
index b10bfcefcc9..daeb71faa92 100644
--- a/src/main/java/org/apache/commons/io/input/SequenceReader.java
+++ b/src/main/java/org/apache/commons/io/input/SequenceReader.java
@@ -108,11 +108,6 @@ public int read() throws IOException {
         return c;
     }
 
-    /*
-     * (non-Javadoc)
-     *
-     * @see Reader#read()
-     */
     @Override
     public int read(final char[] cbuf, int off, int len) throws IOException {
         IOUtils.checkFromIndexSize(cbuf, off, len);
diff --git a/src/main/java/org/apache/commons/io/output/AppendableWriter.java b/src/main/java/org/apache/commons/io/output/AppendableWriter.java
index a6f4ff53fa9..b1ace0b908c 100644
--- a/src/main/java/org/apache/commons/io/output/AppendableWriter.java
+++ b/src/main/java/org/apache/commons/io/output/AppendableWriter.java
@@ -79,6 +79,8 @@ public Writer append(final CharSequence csq) throws IOException {
      * @param start the index of the first character in the subsequence
      * @param end   the index of the character following the last character in the subsequence
      * @return this writer
+     * @throws IndexOutOfBoundsException If {@code start} or {@code end} are negative, {@code start} is greater than
+     *                                   {@code end}, or {@code end} is greater than {@code csq.length()}.
      * @throws IOException If an I/O error occurs.
      */
     @Override
@@ -122,6 +124,8 @@ public T getAppendable() {
      * @param cbuf an array with the characters to write.
      * @param off  offset from which to start writing characters.
      * @param len  number of characters to write.
+     * @throws NullPointerException if the array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code cbuf.length}.
      * @throws IOException If an I/O error occurs.
      */
     @Override
@@ -149,6 +153,8 @@ public void write(final int c) throws IOException {
      * @param str a string.
      * @param off offset from which to start writing characters.
      * @param len number of characters to write.
+     * @throws NullPointerException if the string is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code str.length()}.
      * @throws IOException If an I/O error occurs.
      */
     @Override
diff --git a/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java b/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
index adecd946a3e..2588264e172 100644
--- a/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ChunkedOutputStream.java
@@ -168,6 +168,9 @@ int getChunkSize() {
      * @param data      the data to write.
      * @param srcOffset the offset.
      * @param length    the length of data to write.
+     * @throws NullPointerException if the data is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code srcOffset} or {@code length} are negative,
+     *                                   or if {@code srcOffset + length} is greater than {@code data.length}.
      * @throws IOException if an I/O error occurs.
      */
     @Override
diff --git a/src/main/java/org/apache/commons/io/output/ChunkedWriter.java b/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
index f18553fb776..ed22625b667 100644
--- a/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
+++ b/src/main/java/org/apache/commons/io/output/ChunkedWriter.java
@@ -70,6 +70,9 @@ public ChunkedWriter(final Writer writer, final int chunkSize) {
      * @param data      The data.
      * @param srcOffset the offset.
      * @param length    the number of bytes to write.
+     * @throws NullPointerException if the data is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code srcOffset} or {@code length} are negative,
+     *                                   or if {@code srcOffset + length} is greater than {@code data.length}.
      * @throws IOException If an I/O error occurs.
      */
     @Override
diff --git a/src/main/java/org/apache/commons/io/output/WriterOutputStream.java b/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
index c753ccdce87..d17318f79b6 100644
--- a/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/WriterOutputStream.java
@@ -431,6 +431,7 @@ private void processInput(final boolean endOfInput) throws IOException {
      * Writes bytes from the specified byte array to the stream.
      *
      * @param b the byte array containing the bytes to write.
+     * @throws NullPointerException if the byte array is {@code null}.
      * @throws IOException if an I/O error occurs.
      */
     @Override
@@ -444,6 +445,8 @@ public void write(final byte[] b) throws IOException {
      * @param b   the byte array containing the bytes to write.
      * @param off the start offset in the byte array.
      * @param len the number of bytes to write.
+     * @throws NullPointerException      if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code b.length}.
      * @throws IOException if an I/O error occurs.
      */
     @Override
diff --git a/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java b/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
index 73630a4bca2..873df0238d8 100644
--- a/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
+++ b/src/main/java/org/apache/commons/io/output/XmlStreamWriter.java
@@ -302,6 +302,9 @@ public String getEncoding() {
      * @param cbuf the buffer to write the characters from.
      * @param off The start offset.
      * @param len The number of characters to write.
+     * @throws NullPointerException if the buffer is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative,
+     *                                   or if {@code off + len} is greater than {@code cbuf.length}.
      * @throws IOException if an error occurs detecting the encoding.
      */
     @Override

From c4e4f3b5b09d59d0078a7d8b3f3772dea728e06f Mon Sep 17 00:00:00 2001
From: "Piotr P. Karwasz" <pkarwasz-github@apache.org>
Date: Wed, 1 Oct 2025 22:59:46 +0200
Subject: [PATCH 25/25] fix: `ClosedInputStream` and `ThresholdingOutputStream`
 javadoc

---
 .../org/apache/commons/io/input/ClosedInputStream.java | 10 ++++++----
 .../commons/io/output/ThresholdingOutputStream.java    |  3 +++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/apache/commons/io/input/ClosedInputStream.java b/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
index 5ddb9ea6c9d..11bc7be6e19 100644
--- a/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/ClosedInputStream.java
@@ -79,10 +79,12 @@ public int read() {
     /**
      * Returns {@code -1} to indicate that the stream is closed.
      *
-     * @param b ignored.
-     * @param off ignored.
-     * @param len ignored.
-     * @return always -1.
+     * @param b The buffer to read bytes into.
+     * @param off The start offset.
+     * @param len The number of bytes to read.
+     * @return If len is zero, then {@code 0}; otherwise {@code -1}.
+     * @throws NullPointerException if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code b.length}.
      */
     @Override
     public int read(final byte[] b, final int off, final int len) throws IOException {
diff --git a/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java b/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
index 2efe401910a..742572b2ebc 100644
--- a/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
+++ b/src/main/java/org/apache/commons/io/output/ThresholdingOutputStream.java
@@ -228,6 +228,7 @@ protected void thresholdReached() throws IOException {
      * Writes {@code b.length} bytes from the specified byte array to this output stream.
      *
      * @param b The array of bytes to be written.
+     * @throws NullPointerException if the byte array is {@code null}.
      * @throws IOException if an error occurs.
      */
     @SuppressWarnings("resource") // the underlying stream is managed by a subclass.
@@ -245,6 +246,8 @@ public void write(final byte[] b) throws IOException {
      * @param b The byte array from which the data will be written.
      * @param off The start offset in the byte array.
      * @param len The number of bytes to write.
+     * @throws NullPointerException if the byte array is {@code null}.
+     * @throws IndexOutOfBoundsException if {@code off} or {@code len} are negative, or if {@code off + len} is greater than {@code b.length}.
      * @throws IOException if an error occurs.
      */
     @SuppressWarnings("resource") // the underlying stream is managed by a subclass.