Add ClosedInputStream.INSTANCE and deprecate CLOSED_INPUT_STREAM.

Author: Gary Gregory

src/changes/changes.xml

@@ -72,6 +72,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add BrokenInputStream.INSTANCE.
       </action>
+      <action dev="ggregory" type="add" due-to="Gary Gregory">
+        Add ClosedInputStream.INSTANCE and deprecate CLOSED_INPUT_STREAM.
+      </action>
       <!-- UPDATE -->
       <action dev="ggregory" type="update" due-to="Dependabot">
         Bump Maven Javadoc plugin from 3.2.0 to 3.3.0.

src/main/java/org/apache/commons/io/input/AutoCloseInputStream.java

@@ -63,7 +63,7 @@ public AutoCloseInputStream(final InputStream in) {
     @Override
     public void close() throws IOException {
         in.close();
-        in = ClosedInputStream.CLOSED_INPUT_STREAM;
+        in = ClosedInputStream.INSTANCE;
     }
 
     /**

src/main/java/org/apache/commons/io/input/CloseShieldInputStream.java

@@ -61,7 +61,7 @@ public CloseShieldInputStream(final InputStream inputStream) {
      */
     @Override
     public void close() {
-        in = ClosedInputStream.CLOSED_INPUT_STREAM;
+        in = ClosedInputStream.INSTANCE;
     }
 
 }

src/main/java/org/apache/commons/io/input/ClosedInputStream.java

@@ -21,22 +21,30 @@
 import java.io.InputStream;
 
 /**
- * Closed input stream. This stream returns EOF to all attempts to read
- * something from the stream.
+ * Closed input stream. This stream returns EOF to all attempts to read something from the stream.
  * <p>
- * Typically uses of this class include testing for corner cases in methods
- * that accept input streams and acting as a sentinel value instead of a
- * {@code null} input stream.
+ * Typically uses of this class include testing for corner cases in methods that accept input streams and acting as a
+ * sentinel value instead of a {@code null} input stream.
  * </p>
  *
  * @since 1.4
  */
 public class ClosedInputStream extends InputStream {
 
     /**
-     * A singleton.
+     * The singleton instance.
+     *
+     * @since 2.12.0
+     */
+    public static final ClosedInputStream INSTANCE = new ClosedInputStream();
+
+    /**
+     * The singleton instance.
+     *
+     * @deprecated Use {@link #INSTANCE}.
      */
-    public static final ClosedInputStream CLOSED_INPUT_STREAM = new ClosedInputStream();
+    @Deprecated
+    public static final ClosedInputStream CLOSED_INPUT_STREAM = INSTANCE;
 
     /**
      * Returns -1 to indicate that the stream is closed.

src/main/java/org/apache/commons/io/output/AbstractByteArrayOutputStream.java

@@ -306,7 +306,7 @@ protected <T extends InputStream> InputStream toInputStream(
             final InputStreamConstructor<T> isConstructor) {
         int remaining = count;
         if (remaining == 0) {
-            return ClosedInputStream.CLOSED_INPUT_STREAM;
+            return ClosedInputStream.INSTANCE;
         }
         final List<T> list = new ArrayList<>(buffers.size());
         for (final byte[] buf : buffers) {

src/test/java/org/apache/commons/io/input/TaggedInputStreamTest.java

@@ -36,7 +36,7 @@ public class TaggedInputStreamTest  {
 
     @Test
     public void testEmptyStream() throws IOException {
-        final InputStream stream = new TaggedInputStream(ClosedInputStream.CLOSED_INPUT_STREAM);
+        final InputStream stream = new TaggedInputStream(ClosedInputStream.INSTANCE);
         assertEquals(0, stream.available());
         assertEquals(-1, stream.read());
         assertEquals(-1, stream.read(new byte[1]));
@@ -111,7 +111,7 @@ public void testBrokenStream() {
     @Test
     public void testOtherException() throws Exception {
         final IOException exception = new IOException("test exception");
-        final TaggedInputStream stream = new TaggedInputStream(ClosedInputStream.CLOSED_INPUT_STREAM);
+        final TaggedInputStream stream = new TaggedInputStream(ClosedInputStream.INSTANCE);
 
         assertFalse(stream.isCauseOf(exception));
         assertFalse(stream.isCauseOf(

src/test/java/org/apache/commons/io/input/UncheckedFilterInputStreamTest.java

@@ -125,7 +125,7 @@ public void testReadThrows() {
 
     @Test
     public void testResetThrows() {
-        try (UncheckedFilterInputStream closedReader = UncheckedFilterInputStream.on(ClosedInputStream.CLOSED_INPUT_STREAM)) {
+        try (UncheckedFilterInputStream closedReader = UncheckedFilterInputStream.on(ClosedInputStream.INSTANCE)) {
             closedReader.close();
             assertThrows(UncheckedIOException.class, () -> brokenInputStream.reset());
         }