8196298: Add null Reader and Writer
Reviewed-by: bpb, forax, smarks, alanb, rriggs
Contributed-by: patrick@reini.net
--- a/src/java.base/share/classes/java/io/Reader.java Fri Mar 16 21:40:09 2018 +0100
+++ b/src/java.base/share/classes/java/io/Reader.java Mon Mar 19 09:58:41 2018 -0400
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,7 @@
package java.io;
+import java.nio.CharBuffer;
import java.util.Objects;
/**
@@ -55,6 +56,85 @@
private static final int TRANSFER_BUFFER_SIZE = 8192;
/**
+ * Returns a new {@code Reader} that reads no characters. The returned
+ * stream is initially open. The stream is closed by calling the
+ * {@code close()} method. Subsequent calls to {@code close()} have no
+ * effect.
+ *
+ * <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
+ * 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
+ * throws {@code IOException}.
+ *
+ * <p> The {@link #lock object} used to synchronize operations on the
+ * returned {@code Reader} is not specified.
+ *
+ * @return a {@code Reader} which reads no characters
+ *
+ * @since 11
+ */
+ public static Reader nullReader() {
+ return new Reader() {
+ private volatile boolean closed;
+
+ private void ensureOpen() throws IOException {
+ if (closed) {
+ throw new IOException("Stream closed");
+ }
+ }
+
+ @Override
+ public int read() throws IOException {
+ ensureOpen();
+ return -1;
+ }
+
+ @Override
+ public int read(char[] cbuf, int off, int len) throws IOException {
+ Objects.checkFromIndexSize(off, len, cbuf.length);
+ ensureOpen();
+ if (len == 0) {
+ return 0;
+ }
+ return -1;
+ }
+
+ @Override
+ public int read(CharBuffer target) throws IOException {
+ Objects.requireNonNull(target);
+ ensureOpen();
+ if (target.hasRemaining()) {
+ return -1;
+ }
+ return 0;
+ }
+
+ @Override
+ public long skip(long n) throws IOException {
+ ensureOpen();
+ return 0L;
+ }
+
+ @Override
+ public long transferTo(Writer out) throws IOException {
+ Objects.requireNonNull(out);
+ ensureOpen();
+ return 0L;
+ }
+
+ @Override
+ public void close() {
+ closed = true;
+ }
+ };
+ }
+
+ /**
* The object used to synchronize operations on this stream. For
* efficiency, a character-stream object may use an object other than
* itself to protect critical sections. A subclass should therefore use
--- a/src/java.base/share/classes/java/io/Writer.java Fri Mar 16 21:40:09 2018 +0100
+++ b/src/java.base/share/classes/java/io/Writer.java Mon Mar 19 09:58:41 2018 -0400
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,8 @@
package java.io;
+import java.util.Objects;
+
/**
* Abstract class for writing to character streams. The only methods that a
* subclass must implement are write(char[], int, int), flush(), and close().
@@ -59,6 +61,91 @@
private static final int WRITE_BUFFER_SIZE = 1024;
/**
+ * Returns a new {@code Writer} which discards all characters. The
+ * returned stream is initially open. The stream is closed by calling
+ * the {@code close()} method. Subsequent calls to {@code close()} have
+ * no effect.
+ *
+ * <p> While the stream is open, the {@code append(char)}, {@code
+ * append(CharSequence)}, {@code append(CharSequence, int, int)},
+ * {@code flush()}, {@code write(int)}, {@code write(char[])}, and
+ * {@code write(char[], int, int)} methods do nothing. After the stream
+ * has been closed, these methods all throw {@code IOException}.
+ *
+ * <p> The {@link #lock object} used to synchronize operations on the
+ * returned {@code Writer} is not specified.
+ *
+ * @return a {@code Writer} which discards all characters
+ *
+ * @since 11
+ */
+ public static Writer nullWriter() {
+ return new Writer() {
+ private volatile boolean closed;
+
+ private void ensureOpen() throws IOException {
+ if (closed) {
+ throw new IOException("Stream closed");
+ }
+ }
+
+ @Override
+ public Writer append(char c) throws IOException {
+ ensureOpen();
+ return this;
+ }
+
+ @Override
+ public Writer append(CharSequence csq) throws IOException {
+ ensureOpen();
+ return this;
+ }
+
+ @Override
+ public Writer append(CharSequence csq, int start, int end) throws IOException {
+ ensureOpen();
+ if (csq != null) {
+ Objects.checkFromToIndex(start, end, csq.length());
+ }
+ return this;
+ }
+
+ @Override
+ public void write(int c) throws IOException {
+ ensureOpen();
+ }
+
+ @Override
+ public void write(char[] cbuf, int off, int len) throws IOException {
+ Objects.checkFromIndexSize(off, len, cbuf.length);
+ ensureOpen();
+ }
+
+ @Override
+ public void write(String str) throws IOException {
+ Objects.requireNonNull(str);
+ ensureOpen();
+ }
+
+ @Override
+ public void write(String str, int off, int len) throws IOException {
+ Objects.checkFromIndexSize(off, len, str.length());
+ ensureOpen();
+ }
+
+ @Override
+ public void flush() throws IOException {
+ ensureOpen();
+ }
+
+ @Override
+ public void close() throws IOException {
+ closed = true;
+ }
+ };
+ }
+
+ /**
* The object used to synchronize operations on this stream. For
* efficiency, a character-stream object may use an object other than
* itself to protect critical sections. A subclass should therefore use
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/io/Reader/NullReader.java Mon Mar 19 09:58:41 2018 -0400
@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.io.Reader;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.nio.CharBuffer;
+import java.nio.ReadOnlyBufferException;
+
+import org.testng.annotations.AfterGroups;
+import org.testng.annotations.BeforeGroups;
+import org.testng.annotations.Test;
+
+import static org.testng.Assert.*;
+
+/*
+ * @test
+ * @bug 8196298
+ * @run testng NullReader
+ * @summary Check for expected behavior of Reader.nullReader().
+ */
+public class NullReader {
+ private static Reader openReader;
+ private static Reader closedReader;
+
+ @BeforeGroups(groups = "open")
+ public static void openStream() {
+ openReader = Reader.nullReader();
+ }
+
+ @BeforeGroups(groups = "closed")
+ public static void openAndCloseStream() throws IOException {
+ closedReader = Reader.nullReader();
+ closedReader.close();
+ }
+
+ @AfterGroups(groups = "open")
+ public static void closeStream() throws IOException {
+ openReader.close();
+ }
+
+ @Test(groups = "open")
+ public static void testOpen() {
+ assertNotNull(openReader, "Reader.nullReader() returned null");
+ }
+
+ @Test(groups = "open")
+ public static void testRead() throws IOException {
+ assertEquals(-1, openReader.read(), "read() != -1");
+ }
+
+ @Test(groups = "open")
+ public static void testReadBII() throws IOException {
+ assertEquals(-1, openReader.read(new char[1], 0, 1),
+ "read(char[],int,int) != -1");
+ }
+
+ @Test(groups = "open")
+ public static void testReadBIILenZero() throws IOException {
+ assertEquals(0, openReader.read(new char[1], 0, 0),
+ "read(char[],int,int) != 0");
+ }
+
+ @Test(groups = "open")
+ public static void testReadCharBuffer() throws IOException {
+ CharBuffer charBuffer = CharBuffer.allocate(1);
+ assertEquals(-1, openReader.read(charBuffer),
+ "read(CharBuffer) != -1");
+ }
+
+ @Test(groups = "open")
+ public static void testReadCharBufferZeroRemaining() throws IOException {
+ CharBuffer charBuffer = CharBuffer.allocate(0);
+ assertEquals(0, openReader.read(charBuffer),
+ "read(CharBuffer) != 0");
+ }
+
+ @Test(groups = "open")
+ public static void testSkip() throws IOException {
+ assertEquals(0, openReader.skip(1), "skip() != 0");
+ }
+
+ @Test(groups = "open")
+ public static void testTransferTo() throws IOException {
+ assertEquals(0, openReader.transferTo(new StringWriter(7)),
+ "transferTo() != 0");
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testReadClosed() throws IOException {
+ closedReader.read();
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testReadBIIClosed() throws IOException {
+ closedReader.read(new char[1], 0, 1);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testReadCharBufferClosed() throws IOException {
+ CharBuffer charBuffer = CharBuffer.allocate(0);
+ closedReader.read(charBuffer);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testReadCharBufferZeroRemainingClosed() throws IOException {
+ CharBuffer charBuffer = CharBuffer.allocate(0);
+ closedReader.read(charBuffer);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testSkipClosed() throws IOException {
+ closedReader.skip(1);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testTransferToClosed() throws IOException {
+ closedReader.transferTo(new StringWriter(7));
+ }
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/io/Writer/NullWriter.java Mon Mar 19 09:58:41 2018 -0400
@@ -0,0 +1,167 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.io.IOException;
+import java.io.Writer;
+
+import org.testng.annotations.AfterGroups;
+import org.testng.annotations.BeforeGroups;
+import org.testng.annotations.Test;
+
+import static org.testng.Assert.*;
+
+/*
+ * @test
+ * @bug 8196298
+ * @run testng NullWriter
+ * @summary Check for expected behavior of Writer.nullWriter().
+ */
+public class NullWriter {
+ private static Writer openWriter;
+ private static Writer closedWriter;
+
+ @BeforeGroups(groups = "open")
+ public static void openStream() {
+ openWriter = Writer.nullWriter();
+ }
+
+ @BeforeGroups(groups = "closed")
+ public static void openAndCloseStream() throws IOException {
+ closedWriter = Writer.nullWriter();
+ closedWriter.close();
+ }
+
+ @AfterGroups(groups = "open")
+ public static void closeStream() throws IOException {
+ openWriter.close();
+ }
+
+ @Test(groups = "open")
+ public static void testOpen() {
+ assertNotNull(openWriter, "Writer.nullWriter() returned null");
+ }
+
+ @Test(groups = "open")
+ public static void testAppendChar() throws IOException {
+ assertSame(openWriter, openWriter.append('x'));
+ }
+
+ @Test(groups = "open")
+ public static void testAppendCharSequence() throws IOException {
+ CharSequence cs = "abc";
+ assertSame(openWriter, openWriter.append(cs));
+ }
+
+ @Test(groups = "open")
+ public static void testAppendCharSequenceNull() throws IOException {
+ assertSame(openWriter, openWriter.append(null));
+ }
+
+ @Test(groups = "open")
+ public static void testAppendCharSequenceII() throws IOException {
+ CharSequence cs = "abc";
+ assertSame(openWriter, openWriter.append(cs, 0, 1));
+ }
+
+ @Test(groups = "open")
+ public static void testAppendCharSequenceIINull() throws IOException {
+ assertSame(openWriter, openWriter.append(null, 2, 1));
+ }
+
+ @Test(groups = "open")
+ public static void testFlush() throws IOException {
+ openWriter.flush();
+ }
+
+ @Test(groups = "open")
+ public static void testWrite() throws IOException {
+ openWriter.write(62832);
+ }
+
+ @Test(groups = "open")
+ public static void testWriteString() throws IOException {
+ openWriter.write("");
+ }
+
+ @Test(groups = "open")
+ public static void testWriteStringII() throws IOException {
+ openWriter.write("", 0, 0);
+ }
+
+ @Test(groups = "open")
+ public static void testWriteBII() throws IOException, Exception {
+ openWriter.write(new char[]{(char) 6}, 0, 1);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testAppendCharClosed() throws IOException {
+ closedWriter.append('x');
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testAppendCharSequenceClosed() throws IOException {
+ CharSequence cs = "abc";
+ closedWriter.append(cs);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testAppendCharSequenceNullClosed() throws IOException {
+ closedWriter.append(null);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testAppendCharSequenceIIClosed() throws IOException {
+ CharSequence cs = "abc";
+ closedWriter.append(cs, 0, 1);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testAppendCharSequenceIINullClosed() throws IOException {
+ closedWriter.append(null, 2, 1);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testFlushClosed() throws IOException {
+ closedWriter.flush();
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testWriteClosed() throws IOException {
+ closedWriter.write(62832);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testWriteStringClosed() throws IOException {
+ closedWriter.write("");
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testWriteStringIIClosed() throws IOException {
+ closedWriter.write("", 0, 0);
+ }
+
+ @Test(groups = "closed", expectedExceptions = IOException.class)
+ public static void testWriteBIIClosed() throws IOException {
+ closedWriter.write(new char[]{(char) 6}, 0, 1);
+ }
+}