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;
021
022import org.apache.commons.io.IOUtils;
023
024/**
025 * Appends all data to the famous <strong>/dev/null</strong>.
026 * <p>
027 * This Appendable has no destination (file/socket etc.) and all characters written to it are ignored and lost.
028 * </p>
029 *
030 * @since 2.8.0
031 */
032public class NullAppendable implements Appendable { // NOPMD Class will be final in 3.0.
033
034    /**
035     * A singleton.
036     */
037    public static final NullAppendable INSTANCE = new NullAppendable();
038
039    /** Use the singleton. */
040    private NullAppendable() {
041        // no instances.
042    }
043
044    @Override
045    public Appendable append(final char c) throws IOException {
046        return this;
047    }
048
049    @Override
050    public Appendable append(final CharSequence csq) throws IOException {
051        return this;
052    }
053
054    /**
055     * Does nothing except argument validation, like writing to {@code /dev/null}.
056     *
057     * @param csq   The character sequence from which a subsequence will be
058     *              appended.
059     *              If {@code csq} is {@code null}, it is treated as if it were
060     *              {@code "null"}.
061     * @param start The index of the first character in the subsequence.
062     * @param end   The index of the character following the last character in the
063     *              subsequence.
064     * @return {@code this} instance.
065     * @throws IndexOutOfBoundsException If {@code start} or {@code end} are negative, {@code end} is
066     *                                   greater than {@code csq.length()}, or {@code start} is greater
067     *                                   than {@code end}.
068     */
069    @Override
070    public Appendable append(final CharSequence csq, final int start, final int end) throws IOException {
071        IOUtils.checkFromToIndex(csq, start, end);
072        return this;
073    }
074
075}