    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 {@link File}s that can be read.
    028 * <p>
    029 * Example, showing how to print out a list of the current directory's <em>readable</em> files:
    030 * </p>
    031 * <h2>Using Classic IO</h2>
    032 * <pre>
    033 * File dir = FileUtils.current();
    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 <em>un-readable</em> files:
    042 *
    043 * <pre>
    044 * File dir = FileUtils.current();
    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 <em>read-only</em> files:
    053 *
    054 * <pre>
    055 * File dir = FileUtils.current();
    056 * String[] files = dir.list(CanReadFileFilter.READ_ONLY);
    057 * for (String file : files) {
    058 *     System.out.println(file);
    059 * }
    060 * </pre>
    061 * <h2>Deprecating Serialization</h2>
    062 * <p>
    063 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    064 * </p>
    065 *
    066 * @since 1.3
    067 */
    068public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
    069
    070    /** Singleton instance of <em>readable</em> filter */
    071    public static final IOFileFilter CAN_READ = new CanReadFileFilter();
    072
    073    /** Singleton instance of not <em>readable</em> filter */
    074    public static final IOFileFilter CANNOT_READ = CAN_READ.negate();
    075
    076    /** Singleton instance of <em>read-only</em> filter */
    077    public static final IOFileFilter READ_ONLY = CAN_READ.and(CanWriteFileFilter.CANNOT_WRITE);
    078
    079    private static final long serialVersionUID = 3179904805251622989L;
    080
    081    /**
    082     * Restrictive constructor.
    083     */
    084    protected CanReadFileFilter() {
    085    }
    086
    087    /**
    088     * Checks to see if the file can be read.
    089     *
    090     * @param file the File to check.
    091     * @return {@code true} if the file can be read, otherwise {@code false}.
    092     */
    093    @Override
    094    public boolean accept(final File file) {
    095        return file != null && file.canRead();
    096    }
    097
    098    /**
    099     * Checks to see if the file can be read.
    100     *
    101     * @param file the File to check.
    102     * @param attributes the path's basic attributes (may be null).
    103     * @return {@code true} if the file can be read, otherwise {@code false}.
    104     * @since 2.9.0
    105     */
    106    @Override
    107    public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
    108        return toFileVisitResult(file != null && Files.isReadable(file));
    109    }
    110
    111}