8204930: Reader:nullReader() spec does not match the behavior

Reviewed-by: bpb, rriggs

src/java.base/share/classes/java/io/Reader.java

@@ -63,13 +63,12 @@ public abstract class Reader implements Readable, Closeable {
      *
      * <p> While the stream is open, the {@code read()}, {@code read(char[])},
      * {@code read(char[], int, int)}, {@code read(Charbuffer)}, {@code
-     * ready())}, {@code skip(long)}, and {@code transferTo()} methods all
+     * ready()}, {@code skip(long)}, and {@code transferTo()} methods all
      * behave as if end of stream has been reached. After the stream has been
      * closed, these methods all throw {@code IOException}.
      *
      * <p> The {@code markSupported()} method returns {@code false}.  The
-     * {@code mark()} method does nothing, and the {@code reset()} method
+     * {@code mark()} and {@code reset()} methods throw an {@code IOException}.
-     * throws {@code IOException}.
      *
      * <p> The {@link #lock object} used to synchronize operations on the
      * returned {@code Reader} is not specified.
@@ -114,6 +113,12 @@ public abstract class Reader implements Readable, Closeable {
                 return 0;
             }
 
+            @Override
+            public boolean ready() throws IOException {
+                ensureOpen();
+                return false;
+            }
+
             @Override
             public long skip(long n) throws IOException {
                 ensureOpen();

test/jdk/java/io/Reader/NullReader.java

@@ -35,7 +35,7 @@ import static org.testng.Assert.*;
 
 /*
  * @test
- * @bug 8196298
+ * @bug 8196298 8204930
  * @run testng NullReader
  * @summary Check for expected behavior of Reader.nullReader().
  */
@@ -95,6 +95,11 @@ public class NullReader {
                 "read(CharBuffer) != 0");
     }
 
+    @Test(groups = "open")
+    public static void testReady() throws IOException {
+        assertFalse(openReader.ready());
+    }
+
     @Test(groups = "open")
     public static void testSkip() throws IOException {
         assertEquals(0, openReader.skip(1), "skip() != 0");
@@ -128,6 +133,11 @@ public class NullReader {
         closedReader.read(charBuffer);
     }
 
+    @Test(groups = "closed", expectedExceptions = IOException.class)
+    public static void testReadyClosed() throws IOException {
+        closedReader.ready();
+    }
+
     @Test(groups = "closed", expectedExceptions = IOException.class)
     public static void testSkipClosed() throws IOException {
         closedReader.skip(1);