    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}