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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  import org.apache.commons.io.IOCase;
24  
25  /**
26   * Compare the <b>names</b> of two files for order (see {@link File#getName()}).
27   * <p>
28   * This comparator can be used to sort lists or arrays of files
29   * by their name either in a case-sensitive, case-insensitive or
30   * system dependent case-sensitive way. A number of singleton instances
31   * are provided for the various case sensitivity options (using {@link IOCase})
32   * and the reverse of those options.
33   * </p>
34   * <p>
35   * Example of a <i>case-sensitive</i> file name sort using the
36   * {@link #NAME_COMPARATOR} singleton instance:
37   * </p>
38   * <pre>
39   *       List&lt;File&gt; list = ...
40   *       ((AbstractFileComparator) NameFileComparator.NAME_COMPARATOR).sort(list);
41   * </pre>
42   * <p>
43   * Example of a <i>reverse case-insensitive</i> file name sort using the
44   * {@link #NAME_INSENSITIVE_REVERSE} singleton instance:
45   * </p>
46   * <pre>
47   *       File[] array = ...
48   *       ((AbstractFileComparator) NameFileComparator.NAME_INSENSITIVE_REVERSE).sort(array);
49   * </pre>
50   * <h2>Deprecating Serialization</h2>
51   * <p>
52   * <em>Serialization is deprecated and will be removed in 3.0.</em>
53   * </p>
54   *
55   * @since 1.4
56   */
57  public class NameFileComparator extends AbstractFileComparator implements Serializable {
58  
59      private static final long serialVersionUID = 8397947749814525798L;
60  
61      /** Case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
62      public static final Comparator<File> NAME_COMPARATOR = new NameFileComparator();
63  
64      /** Reverse case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
65      public static final Comparator<File> NAME_REVERSE = new ReverseFileComparator(NAME_COMPARATOR);
66  
67      /** Case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
68      public static final Comparator<File> NAME_INSENSITIVE_COMPARATOR = new NameFileComparator(IOCase.INSENSITIVE);
69  
70      /** Reverse case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
71      public static final Comparator<File> NAME_INSENSITIVE_REVERSE = new ReverseFileComparator(NAME_INSENSITIVE_COMPARATOR);
72  
73      /** System sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
74      public static final Comparator<File> NAME_SYSTEM_COMPARATOR = new NameFileComparator(IOCase.SYSTEM);
75  
76      /** Reverse system sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
77      public static final Comparator<File> NAME_SYSTEM_REVERSE = new ReverseFileComparator(NAME_SYSTEM_COMPARATOR);
78  
79      /** Whether the comparison is case-sensitive. */
80      private final IOCase ioCase;
81  
82      /**
83       * Constructs a case-sensitive file name comparator instance.
84       */
85      public NameFileComparator() {
86          this.ioCase = IOCase.SENSITIVE;
87      }
88  
89      /**
90       * Constructs a file name comparator instance with the specified case-sensitivity.
91       *
92       * @param ioCase  how to handle case sensitivity, null means case-sensitive
93       */
94      public NameFileComparator(final IOCase ioCase) {
95          this.ioCase = IOCase.value(ioCase, IOCase.SENSITIVE);
96      }
97  
98      /**
99       * Compares the names of two files with the specified case sensitivity.
100      *
101      * @param file1 The first file to compare
102      * @param file2 The second file to compare
103      * @return a negative value if the first file's name
104      * is less than the second, zero if the names are the
105      * same and a positive value if the first files name
106      * is greater than the second file.
107      */
108     @Override
109     public int compare(final File file1, final File file2) {
110         return ioCase.checkCompareTo(file1.getName(), file2.getName());
111     }
112 
113     /**
114      * String representation of this file comparator.
115      *
116      * @return String representation of this file comparator
117      */
118     @Override
119     public String toString() {
120         return super.toString() + "[ioCase=" + ioCase + "]";
121     }
122 }