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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   */
17  package org.apache.commons.io.filefilter;
18  
19  import java.io.File;
20  
21  /**
22   * This filter accepts <code>File</code>s that can be read.
23   * <p>
24   * Example, showing how to print out a list of the 
25   * current directory's <i>readable</i> files:
26   *
27   * <pre>
28   * File dir = new File(".");
29   * String[] files = dir.list( CanReadFileFilter.CAN_READ );
30   * for ( int i = 0; i &lt; files.length; i++ ) {
31   *     System.out.println(files[i]);
32   * }
33   * </pre>
34   *
35   * <p>
36   * Example, showing how to print out a list of the 
37   * current directory's <i>un-readable</i> files:
38   *
39   * <pre>
40   * File dir = new File(".");
41   * String[] files = dir.list( CanReadFileFilter.CANNOT_READ );
42   * for ( int i = 0; i &lt; files.length; i++ ) {
43   *     System.out.println(files[i]);
44   * }
45   * </pre>
46   *
47   * <p>
48   * Example, showing how to print out a list of the 
49   * current directory's <i>read-only</i> files:
50   *
51   * <pre>
52   * File dir = new File(".");
53   * String[] files = dir.list( CanReadFileFilter.READ_ONLY );
54   * for ( int i = 0; i &lt; files.length; i++ ) {
55   *     System.out.println(files[i]);
56   * }
57   * </pre>
58   *
59   * @since Commons IO 1.3
60   * @version $Revision: 437567 $
61   */
62  public class CanReadFileFilter extends AbstractFileFilter {
63      
64      /** Singleton instance of <i>readable</i> filter */
65      public static final IOFileFilter CAN_READ = new CanReadFileFilter();
66  
67      /** Singleton instance of not <i>readable</i> filter */
68      public static final IOFileFilter CANNOT_READ = new NotFileFilter(CAN_READ);
69      
70      /** Singleton instance of <i>read-only</i> filter */
71      public static final IOFileFilter READ_ONLY = new AndFileFilter(CAN_READ,
72                                                  CanWriteFileFilter.CANNOT_WRITE);
73      
74      /**
75       * Restrictive consructor.
76       */
77      protected CanReadFileFilter() {
78      }
79      
80      /**
81       * Checks to see if the file can be read.
82       * 
83       * @param file  the File to check.
84       * @return <code>true</code> if the file can be
85       *  read, otherwise <code>false</code>.
86       */
87      public boolean accept(File file) {
88          return file.canRead();
89      }
90      
91  }