    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;
    021
    022/**
    023 * This filter accepts <code>File</code>s that can be read.
    024 * <p>
    025 * Example, showing how to print out a list of the
    026 * current directory's <i>readable</i> files:
    027 *
    028 * <pre>
    029 * File dir = new File(".");
    030 * String[] files = dir.list( CanReadFileFilter.CAN_READ );
    031 * for ( int i = 0; i &lt; files.length; i++ ) {
    032 *     System.out.println(files[i]);
    033 * }
    034 * </pre>
    035 *
    036 * <p>
    037 * Example, showing how to print out a list of the
    038 * current directory's <i>un-readable</i> files:
    039 *
    040 * <pre>
    041 * File dir = new File(".");
    042 * String[] files = dir.list( CanReadFileFilter.CANNOT_READ );
    043 * for ( int i = 0; i &lt; files.length; i++ ) {
    044 *     System.out.println(files[i]);
    045 * }
    046 * </pre>
    047 *
    048 * <p>
    049 * Example, showing how to print out a list of the
    050 * current directory's <i>read-only</i> files:
    051 *
    052 * <pre>
    053 * File dir = new File(".");
    054 * String[] files = dir.list( CanReadFileFilter.READ_ONLY );
    055 * for ( int i = 0; i &lt; files.length; i++ ) {
    056 *     System.out.println(files[i]);
    057 * }
    058 * </pre>
    059 *
    060 * @since 1.3
    061 *
    062 */
    063public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
    064
    065    private static final long serialVersionUID = 3179904805251622989L;
    066
    067    /** Singleton instance of <i>readable</i> filter */
    068    public static final IOFileFilter CAN_READ = new CanReadFileFilter();
    069
    070    /** Singleton instance of not <i>readable</i> filter */
    071    public static final IOFileFilter CANNOT_READ = new NotFileFilter(CAN_READ);
    072
    073    /** Singleton instance of <i>read-only</i> filter */
    074    public static final IOFileFilter READ_ONLY = new AndFileFilter(CAN_READ,
    075                                                CanWriteFileFilter.CANNOT_WRITE);
    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
    088     *  read, otherwise {@code false}.
    089     */
    090    @Override
    091    public boolean accept(final File file) {
    092        return file.canRead();
    093    }
    094
    095}