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 * @version $Id: CanReadFileFilter.java 1307462 2012-03-30 15:13:11Z ggregory $
062 */
063public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
064    
065    /** Singleton instance of <i>readable</i> filter */
066    public static final IOFileFilter CAN_READ = new CanReadFileFilter();
067
068    /** Singleton instance of not <i>readable</i> filter */
069    public static final IOFileFilter CANNOT_READ = new NotFileFilter(CAN_READ);
070    
071    /** Singleton instance of <i>read-only</i> filter */
072    public static final IOFileFilter READ_ONLY = new AndFileFilter(CAN_READ,
073                                                CanWriteFileFilter.CANNOT_WRITE);
074    
075    /**
076     * Restrictive consructor.
077     */
078    protected CanReadFileFilter() {
079    }
080    
081    /**
082     * Checks to see if the file can be read.
083     * 
084     * @param file  the File to check.
085     * @return {@code true} if the file can be
086     *  read, otherwise {@code false}.
087     */
088    @Override
089    public boolean accept(File file) {
090        return file.canRead();
091    }
092    
093}