Add ClosedOutputStream.INSTANCE and deprecate CLOSED_OUTPUT_STREAM.

Author: Gary Gregory

src/changes/changes.xml

@@ -81,6 +81,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add BrokenWriter.INSTANCE.
       </action>
+      <action dev="ggregory" type="add" due-to="Gary Gregory">
+        Add ClosedOutputStream.INSTANCE and deprecate CLOSED_OUTPUT_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/output/CloseShieldOutputStream.java

@@ -61,7 +61,7 @@ public CloseShieldOutputStream(final OutputStream outputStream) {
      */
     @Override
     public void close() {
-        out = ClosedOutputStream.CLOSED_OUTPUT_STREAM;
+        out = ClosedOutputStream.INSTANCE;
     }
 
 }

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

@@ -31,9 +31,19 @@
 public class ClosedOutputStream extends OutputStream {
 
     /**
-     * A singleton.
+     * The singleton instance.
+     *
+     * @since 2.12.0
+     */
+    public static final ClosedOutputStream INSTANCE = new ClosedOutputStream();
+
+    /**
+     * The singleton instance.
+     *
+     * @deprecated Use {@link #INSTANCE}.
      */
-    public static final ClosedOutputStream CLOSED_OUTPUT_STREAM = new ClosedOutputStream();
+    @Deprecated
+    public static final ClosedOutputStream CLOSED_OUTPUT_STREAM = INSTANCE;
 
     /**
      * Throws an {@link IOException} to indicate that the stream is closed.

src/test/java/org/apache/commons/io/output/TaggedOutputStreamTest.java

@@ -103,7 +103,7 @@ public void testBrokenStream() {
     @Test
     public void testOtherException() throws Exception {
         final IOException exception = new IOException("test exception");
-        try (final TaggedOutputStream stream = new TaggedOutputStream(ClosedOutputStream.CLOSED_OUTPUT_STREAM)) {
+        try (final TaggedOutputStream stream = new TaggedOutputStream(ClosedOutputStream.INSTANCE)) {
 
             assertFalse(stream.isCauseOf(exception));
             assertFalse(stream.isCauseOf(new TaggedIOException(exception, UUID.randomUUID())));