Add ClosedReader.INSTANCE and deprecate CLOSED_READER.

Author: Gary Gregory

src/changes/changes.xml

@@ -75,6 +75,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add ClosedInputStream.INSTANCE and deprecate CLOSED_INPUT_STREAM.
       </action>
+      <action dev="ggregory" type="add" due-to="Gary Gregory">
+        Add ClosedReader.INSTANCE and deprecate CLOSED_READER.
+      </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/CloseShieldReader.java

@@ -60,7 +60,7 @@ public CloseShieldReader(final Reader reader) {
      */
     @Override
     public void close() {
-        in = ClosedReader.CLOSED_READER;
+        in = ClosedReader.INSTANCE;
     }
 
 }

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

@@ -33,16 +33,26 @@
 public class ClosedReader extends Reader {
 
     /**
-     * A singleton.
+     * The singleton instance.
+     *
+     * @since 2.12.0
+     */
+    public static final ClosedReader INSTANCE = new ClosedReader();
+
+    /**
+     * The singleton instance.
+     *
+     * @deprecated {@link #INSTANCE}.
      */
-    public static final ClosedReader CLOSED_READER = new ClosedReader();
+    @Deprecated
+    public static final ClosedReader CLOSED_READER = INSTANCE;
 
     /**
      * Returns -1 to indicate that the stream is closed.
      *
      * @param cbuf ignored
-     * @param off  ignored
-     * @param len  ignored
+     * @param off ignored
+     * @param len ignored
      * @return always -1
      */
     @Override

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

@@ -36,7 +36,7 @@ public class TaggedReaderTest {
 
     @Test
     public void testEmptyReader() throws IOException {
-        try (final Reader reader = new TaggedReader(ClosedReader.CLOSED_READER)) {
+        try (final Reader reader = new TaggedReader(ClosedReader.INSTANCE)) {
             assertFalse(reader.ready());
             assertEquals(-1, reader.read());
             assertEquals(-1, reader.read(new char[1]));
@@ -109,7 +109,7 @@ public void testBrokenReader() {
     @Test
     public void testOtherException() throws Exception {
         final IOException exception = new IOException("test exception");
-        try (final TaggedReader reader = new TaggedReader(ClosedReader.CLOSED_READER)) {
+        try (final TaggedReader reader = new TaggedReader(ClosedReader.INSTANCE)) {
 
             assertFalse(reader.isCauseOf(exception));
             assertFalse(reader.isCauseOf(new TaggedIOException(exception, UUID.randomUUID())));

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

@@ -74,7 +74,7 @@ public void testMarkReset() {
 
     @Test
     public void testMarkThrows() {
-        try (UncheckedBufferedReader closedReader = UncheckedBufferedReader.on(ClosedReader.CLOSED_READER)) {
+        try (UncheckedBufferedReader closedReader = UncheckedBufferedReader.on(ClosedReader.INSTANCE)) {
             closedReader.close();
             assertThrows(UncheckedIOException.class, () -> closedReader.mark(1));
         }
@@ -191,7 +191,7 @@ public void testReadyThrows() {
 
     @Test
     public void testResetThrows() {
-        try (UncheckedBufferedReader closedReader = UncheckedBufferedReader.on(ClosedReader.CLOSED_READER)) {
+        try (UncheckedBufferedReader closedReader = UncheckedBufferedReader.on(ClosedReader.INSTANCE)) {
             closedReader.close();
             assertThrows(UncheckedIOException.class, () -> ucBrokenReader.reset());
         }

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

@@ -67,7 +67,7 @@ public void testMarkReset() {
 
     @Test
     public void testMarkThrows() {
-        try (UncheckedFilterReader closedReader = UncheckedFilterReader.on(ClosedReader.CLOSED_READER)) {
+        try (UncheckedFilterReader closedReader = UncheckedFilterReader.on(ClosedReader.INSTANCE)) {
             closedReader.close();
             assertThrows(UncheckedIOException.class, () -> closedReader.mark(1));
         }
@@ -170,7 +170,7 @@ public void testReadyThrows() {
 
     @Test
     public void testResetThrows() {
-        try (UncheckedFilterReader closedReader = UncheckedFilterReader.on(ClosedReader.CLOSED_READER)) {
+        try (UncheckedFilterReader closedReader = UncheckedFilterReader.on(ClosedReader.INSTANCE)) {
             closedReader.close();
             assertThrows(UncheckedIOException.class, () -> ucBrokenReader.reset());
         }