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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 are hidden.
23   * <p>
24   * Example, showing how to print out a list of the
25   * current directory's <i>hidden</i> files:
26   *
27   * <pre>
28   * File dir = new File(".");
29   * String[] files = dir.list( HiddenFileFilter.HIDDEN );
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>visible</i> (i.e. not hidden) files:
38   *
39   * <pre>
40   * File dir = new File(".");
41   * String[] files = dir.list( HiddenFileFilter.VISIBLE );
42   * for ( int i = 0; i &lt; files.length; i++ ) {
43   *     System.out.println(files[i]);
44   * }
45   * </pre>
46   *
47   * @since Commons IO 1.3
48   * @version $Revision: 437567 $
49   */
50  public class HiddenFileFilter extends AbstractFileFilter {
51      
52      /** Singleton instance of <i>hidden</i> filter */
53      public static final IOFileFilter HIDDEN  = new HiddenFileFilter();
54      
55      /** Singleton instance of <i>visible</i> filter */
56      public static final IOFileFilter VISIBLE = new NotFileFilter(HIDDEN);
57      
58      /**
59       * Restrictive consructor.
60       */
61      protected HiddenFileFilter() {
62      }
63      
64      /**
65       * Checks to see if the file is hidden.
66       * 
67       * @param file  the File to check
68       * @return <code>true</code> if the file is
69       *  <i>hidden</i>, otherwise <code>false</code>.
70       */
71      public boolean accept(File file) {
72          return file.isHidden();
73      }
74      
75  }