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 *      https://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 */
017
018package org.apache.commons.io.output;
019
020import java.io.IOException;
021import java.io.Writer;
022import java.util.Arrays;
023
024/**
025 * Throws an IOException on all attempts to write with {@link #close()} implemented as a noop.
026 * <p>
027 * Typically uses of this class include testing for corner cases in methods that accept a writer and acting as a sentinel value instead of a {@code null}
028 * writer.
029 * </p>
030 *
031 * @since 2.7
032 */
033public class ClosedWriter extends Writer {
034
035    /**
036     * The singleton instance.
037     *
038     * @since 2.12.0
039     */
040    public static final ClosedWriter INSTANCE = new ClosedWriter();
041    /**
042     * The singleton instance.
043     *
044     * @deprecated Use {@link #INSTANCE}.
045     */
046    @Deprecated
047    public static final ClosedWriter CLOSED_WRITER = INSTANCE;
048
049    /**
050     * Construct a new instance.
051     */
052    public ClosedWriter() {
053        // empty
054    }
055
056    @Override
057    public void close() throws IOException {
058        // noop
059    }
060
061    /**
062     * Throws an {@link IOException} to indicate that the stream is closed.
063     *
064     * @throws IOException always thrown
065     */
066    @Override
067    public void flush() throws IOException {
068        throw new IOException("flush() failed: stream is closed");
069    }
070
071    /**
072     * Throws an {@link IOException} to indicate that the writer is closed.
073     *
074     * @param cbuf ignored.
075     * @param off  ignored.
076     * @param len  ignored.
077     * @throws IOException always thrown.
078     */
079    @Override
080    public void write(final char[] cbuf, final int off, final int len) throws IOException {
081        throw new IOException(String.format("write(%s, %d, %d) failed: stream is closed", Arrays.toString(cbuf), off, len));
082    }
083}