    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 */
    017package org.apache.commons.io.output;
    018
    019import java.io.IOException;
    020import java.io.Writer;
    021
    022/**
    023 * Throws an IOException 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     * The singleton instance.
    035     *
    036     * @since 2.12.0
    037     */
    038    public static final ClosedWriter INSTANCE = new ClosedWriter();
    039
    040    /**
    041     * The singleton instance.
    042     *
    043     * @deprecated Use {@link #INSTANCE}.
    044     */
    045    @Deprecated
    046    public static final ClosedWriter CLOSED_WRITER = INSTANCE;
    047
    048    /**
    049     * Construct a new instance.
    050     */
    051    public ClosedWriter() {
    052        // empty
    053    }
    054
    055    @Override
    056    public void close() throws IOException {
    057        // noop
    058    }
    059
    060    /**
    061     * Throws an {@link IOException} to indicate that the stream is closed.
    062     *
    063     * @throws IOException always thrown
    064     */
    065    @Override
    066    public void flush() throws IOException {
    067        throw new IOException("flush() failed: stream is closed");
    068    }
    069
    070    /**
    071     * Throws an {@link IOException} to indicate that the writer is closed.
    072     *
    073     * @param cbuf ignored
    074     * @param off ignored
    075     * @param len ignored
    076     * @throws IOException always thrown
    077     */
    078    @Override
    079    public void write(final char[] cbuf, final int off, final int len) throws IOException {
    080        throw new IOException("write(" + new String(cbuf) + ", " + off + ", " + len + ") failed: stream is closed");
    081    }
    082}