1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17package org.apache.commons.io.filefilter;
18
19import java.io.File;
20import java.io.Serializable;
21
22/**
23 * This filter accepts <code>File</code>s that can be read.
24 * <p>
25 * Example, showing how to print out a list of the
26 * current directory's <i>readable</i> files:
27 *
28 * <pre>
29 * File dir = new File(".");
30 * String[] files = dir.list( CanReadFileFilter.CAN_READ );
31 * for ( int i = 0; i &lt; files.length; i++ ) {
32 *     System.out.println(files[i]);
33 * }
34 * </pre>
35 *
36 * <p>
37 * Example, showing how to print out a list of the
38 * current directory's <i>un-readable</i> files:
39 *
40 * <pre>
41 * File dir = new File(".");
42 * String[] files = dir.list( CanReadFileFilter.CANNOT_READ );
43 * for ( int i = 0; i &lt; files.length; i++ ) {
44 *     System.out.println(files[i]);
45 * }
46 * </pre>
47 *
48 * <p>
49 * Example, showing how to print out a list of the
50 * current directory's <i>read-only</i> files:
51 *
52 * <pre>
53 * File dir = new File(".");
54 * String[] files = dir.list( CanReadFileFilter.READ_ONLY );
55 * for ( int i = 0; i &lt; files.length; i++ ) {
56 *     System.out.println(files[i]);
57 * }
58 * </pre>
59 *
60 * @since Commons IO 1.3
61 * @version $Revision: 587916 $
62 */
63public class CanReadFileFilter extends AbstractFileFilter implements Serializable {
64
65    /** Singleton instance of <i>readable</i> filter */
66    public static final IOFileFilter CAN_READ = new CanReadFileFilter();
67
68    /** Singleton instance of not <i>readable</i> filter */
69    public static final IOFileFilter CANNOT_READ = new NotFileFilter(CAN_READ);
70
71    /** Singleton instance of <i>read-only</i> filter */
72    public static final IOFileFilter READ_ONLY = new AndFileFilter(CAN_READ,
73                                                CanWriteFileFilter.CANNOT_WRITE);
74
75    /**
76     * Restrictive consructor.
77     */
78    protected CanReadFileFilter() {
79    }
80
81    /**
82     * Checks to see if the file can be read.
83     *
84     * @param file  the File to check.
85     * @return <code>true</code> if the file can be
86     *  read, otherwise <code>false</code>.
87     */
88    public boolean accept(File file) {
89        return file.canRead();
90    }
91
92}
93