    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}