001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.output;
018
019import java.io.IOException;
020import java.io.Writer;
021
022/**
023 * Throws an exception on all attempts to write with {@link #close()} implemented as a noop.
024 * <p>
025 * Typically uses of this class include testing for corner cases in methods that accept a writer and acting as a
026 * sentinel value instead of a {@code null} writer.
027 * </p>
028 *
029 * @since 2.7
030 */
031public class ClosedWriter extends Writer {
032
033    /**
034     * A singleton.
035     */
036    public static final ClosedWriter CLOSED_WRITER = new ClosedWriter();
037
038    /**
039     * Throws an {@link IOException} to indicate that the writer is closed.
040     *
041     * @param cbuf ignored
042     * @param off ignored
043     * @param len ignored
044     * @throws IOException always thrown
045     */
046    @Override
047    public void write(final char[] cbuf, final int off, final int len) throws IOException {
048        throw new IOException("write(" + new String(cbuf) + ", " + off + ", " + len + ") failed: stream is closed");
049    }
050
051    /**
052     * Throws an {@link IOException} to indicate that the stream is closed.
053     *
054     * @throws IOException always thrown
055     */
056    @Override
057    public void flush() throws IOException {
058        throw new IOException("flush() failed: stream is closed");
059    }
060
061    @Override
062    public void close() throws IOException {
063        // noop
064    }
065}