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    /**
043     * The singleton instance.
044     *
045     * @deprecated Use {@link #INSTANCE}.
046     */
047    @Deprecated
048    public static final ClosedWriter CLOSED_WRITER = INSTANCE;
049
050    /**
051     * Construct a new instance.
052     */
053    public ClosedWriter() {
054        // empty
055    }
056
057    @Override
058    public void close() throws IOException {
059        // noop
060    }
061
062    /**
063     * Throws an {@link IOException} to indicate that the stream is closed.
064     *
065     * @throws IOException always thrown.
066     */
067    @Override
068    public void flush() throws IOException {
069        throw new IOException("flush() failed: stream is closed");
070    }
071
072    /**
073     * Throws an {@link IOException} to indicate that the writer is closed.
074     *
075     * @param cbuf ignored.
076     * @param off  ignored.
077     * @param len  ignored.
078     * @throws IOException always thrown.
079     */
080    @Override
081    public void write(final char[] cbuf, final int off, final int len) throws IOException {
082        throw new IOException(String.format("write(%s, %d, %d) failed: stream is closed", Arrays.toString(cbuf), off, len));
083    }
084}