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.filefilter;
018
019import java.io.File;
020import java.io.Serializable;
021import java.nio.file.FileVisitResult;
022import java.nio.file.Files;
023import java.nio.file.Path;
024import java.nio.file.attribute.BasicFileAttributes;
025
026/**
027 * This filter accepts {@code File}s that can be read.
028 * <p>
029 * Example, showing how to print out a list of the current directory's <i>readable</i> files:
030 * </p>
031 * <h2>Using Classic IO</h2>
032 * <pre>
033 * File dir = new File(".");
034 * String[] files = dir.list(CanReadFileFilter.CAN_READ);
035 * for (String file : files) {
036 *     System.out.println(file);
037 * }
038 * </pre>
039 *
040 * <p>
041 * Example, showing how to print out a list of the current directory's <i>un-readable</i> files:
042 *
043 * <pre>
044 * File dir = new File(".");
045 * String[] files = dir.list(CanReadFileFilter.CANNOT_READ);
046 * for (String file : files) {
047 *     System.out.println(file);
048 * }
049 * </pre>
050 *
051 * <p>
052 * Example, showing how to print out a list of the current directory's <i>read-only</i> files:
053 *
054 * <pre>
055 * File dir = new File(".");
056 * String[] files = dir.list(CanReadFileFilter.READ_ONLY);
057 * for (String file : files) {
058 *     System.out.println(file);
059 * }
060 * </pre>
061 *
062 * @since 1.3
063 */
064public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
065
066    /** Singleton instance of <i>readable</i> filter */
067    public static final IOFileFilter CAN_READ = new CanReadFileFilter();
068
069    /** Singleton instance of not <i>readable</i> filter */
070    public static final IOFileFilter CANNOT_READ = CAN_READ.negate();
071
072    /** Singleton instance of <i>read-only</i> filter */
073    public static final IOFileFilter READ_ONLY = CAN_READ.and(CanWriteFileFilter.CANNOT_WRITE);
074
075    private static final long serialVersionUID = 3179904805251622989L;
076
077    /**
078     * Restrictive constructor.
079     */
080    protected CanReadFileFilter() {
081    }
082
083    /**
084     * Checks to see if the file can be read.
085     *
086     * @param file the File to check.
087     * @return {@code true} if the file can be read, otherwise {@code false}.
088     */
089    @Override
090    public boolean accept(final File file) {
091        return file.canRead();
092    }
093
094    /**
095     * Checks to see if the file can be read.
096     * @param file the File to check.
097     *
098     * @return {@code true} if the file can be read, otherwise {@code false}.
099     * @since 2.9.0
100     */
101    @Override
102    public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
103        return toFileVisitResult(Files.isReadable(file), file);
104    }
105
106}