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.input;
018
019import static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.IOException;
022import java.io.Reader;
023
024import org.apache.commons.io.IOUtils;
025
026/**
027 * Always returns {@link IOUtils#EOF} to all attempts to read something from it.
028 * <p>
029 * Typically uses of this class include testing for corner cases in methods that accept readers and acting as a sentinel
030 * value instead of a {@code null} reader.
031 * </p>
032 *
033 * @since 2.7
034 */
035public class ClosedReader extends Reader {
036
037    /**
038     * The singleton instance.
039     *
040     * @since 2.12.0
041     */
042    public static final ClosedReader INSTANCE = new ClosedReader();
043
044    /**
045     * The singleton instance.
046     *
047     * @deprecated {@link #INSTANCE}.
048     */
049    @Deprecated
050    public static final ClosedReader CLOSED_READER = INSTANCE;
051
052    @Override
053    public void close() throws IOException {
054        // noop
055    }
056
057    /**
058     * Returns -1 to indicate that the stream is closed.
059     *
060     * @param cbuf ignored
061     * @param off ignored
062     * @param len ignored
063     * @return always -1
064     */
065    @Override
066    public int read(final char[] cbuf, final int off, final int len) {
067        return EOF;
068    }
069
070}