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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.comparator;
18  
19  import java.io.File;
20  import java.io.Serializable;
21  import java.util.Comparator;
22  
23  /**
24   * Compare two files using the {@link File#isDirectory()} method.
25   * <p>
26   * This comparator can be used to sort lists or arrays by directories and files.
27   * <p>
28   * Example of sorting a list of files/directories using the
29   * {@link #DIRECTORY_COMPARATOR} singleton instance:
30   * <pre>
31   *       List&lt;File&gt; list = ...
32   *       ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_COMPARATOR).sort(list);
33   * </pre>
34   * <p>
35   * Example of doing a <i>reverse</i> sort of an array of files/directories using the
36   * {@link #DIRECTORY_REVERSE} singleton instance:
37   * <pre>
38   *       File[] array = ...
39   *       ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_REVERSE).sort(array);
40   * </pre>
41   * <p>
42   *
43   * @version $Id: DirectoryFileComparator.java 1642757 2014-12-01 21:09:30Z sebb $
44   * @since 2.0
45   */
46  public class DirectoryFileComparator extends AbstractFileComparator implements Serializable {
47  
48      private static final long serialVersionUID = 296132640160964395L;
49  
50      /** Singleton default comparator instance */
51      public static final Comparator<File> DIRECTORY_COMPARATOR = new DirectoryFileComparator();
52  
53      /** Singleton reverse default comparator instance */
54      public static final Comparator<File> DIRECTORY_REVERSE = new ReverseComparator(DIRECTORY_COMPARATOR);
55  
56      /**
57       * Compare the two files using the {@link File#isDirectory()} method.
58       * 
59       * @param file1 The first file to compare
60       * @param file2 The second file to compare
61       * @return the result of calling file1's
62       * {@link File#compareTo(File)} with file2 as the parameter.
63       */
64      public int compare(final File file1, final File file2) {
65          return getType(file1) - getType(file2);
66      }
67  
68      /**
69       * Convert type to numeric value.
70       *
71       * @param file The file
72       * @return 1 for directories and 2 for files
73       */
74      private int getType(final File file) {
75          if (file.isDirectory()) {
76              return 1;
77          } else {
78              return 2;
79          }
80      }
81  }