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.FilenameUtils;
24 import org.apache.commons.io.IOCase;
25
26 /**
27 * Compare the file name <b>extensions</b> for order
28 * (see {@link FilenameUtils#getExtension(String)}).
29 * <p>
30 * This comparator can be used to sort lists or arrays of files
31 * by their file extension either in a case-sensitive, case-insensitive or
32 * system dependent case-sensitive way. A number of singleton instances
33 * are provided for the various case sensitivity options (using {@link IOCase})
34 * and the reverse of those options.
35 * </p>
36 * <p>
37 * Example of a <i>case-sensitive</i> file extension sort using the
38 * {@link #EXTENSION_COMPARATOR} singleton instance:
39 * </p>
40 * <pre>
41 * List<File> list = ...
42 * ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_COMPARATOR).sort(list);
43 * </pre>
44 * <p>
45 * Example of a <i>reverse case-insensitive</i> file extension sort using the
46 * {@link #EXTENSION_INSENSITIVE_REVERSE} singleton instance:
47 * </p>
48 * <pre>
49 * File[] array = ...
50 * ((AbstractFileComparator) ExtensionFileComparator.EXTENSION_INSENSITIVE_REVERSE).sort(array);
51 * </pre>
52 * <h2>Deprecating Serialization</h2>
53 * <p>
54 * <em>Serialization is deprecated and will be removed in 3.0.</em>
55 * </p>
56 *
57 * @since 1.4
58 */
59 public class ExtensionFileComparator extends AbstractFileComparator implements Serializable {
60
61 private static final long serialVersionUID = 1928235200184222815L;
62
63 /** Case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */
64 public static final Comparator<File> EXTENSION_COMPARATOR = new ExtensionFileComparator();
65
66 /** Reverse case-sensitive extension comparator instance (see {@link IOCase#SENSITIVE}) */
67 public static final Comparator<File> EXTENSION_REVERSE = new ReverseFileComparator(EXTENSION_COMPARATOR);
68
69 /** Case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */
70 public static final Comparator<File> EXTENSION_INSENSITIVE_COMPARATOR
71 = new ExtensionFileComparator(IOCase.INSENSITIVE);
72
73 /** Reverse case-insensitive extension comparator instance (see {@link IOCase#INSENSITIVE}) */
74 public static final Comparator<File> EXTENSION_INSENSITIVE_REVERSE
75 = new ReverseFileComparator(EXTENSION_INSENSITIVE_COMPARATOR);
76
77 /** System sensitive extension comparator instance (see {@link IOCase#SYSTEM}) */
78 public static final Comparator<File> EXTENSION_SYSTEM_COMPARATOR = new ExtensionFileComparator(IOCase.SYSTEM);
79
80 /** Reverse system sensitive path comparator instance (see {@link IOCase#SYSTEM}) */
81 public static final Comparator<File> EXTENSION_SYSTEM_REVERSE = new ReverseFileComparator(EXTENSION_SYSTEM_COMPARATOR);
82
83 /** Whether the comparison is case-sensitive. */
84 private final IOCase ioCase;
85
86 /**
87 * Constructs a case-sensitive file extension comparator instance.
88 */
89 public ExtensionFileComparator() {
90 this.ioCase = IOCase.SENSITIVE;
91 }
92
93 /**
94 * Constructs a file extension comparator instance with the specified case-sensitivity.
95 *
96 * @param ioCase how to handle case sensitivity, null means case-sensitive
97 */
98 public ExtensionFileComparator(final IOCase ioCase) {
99 this.ioCase = IOCase.value(ioCase, IOCase.SENSITIVE);
100 }
101
102 /**
103 * Compares the extensions of two files the specified case sensitivity.
104 *
105 * @param file1 The first file to compare
106 * @param file2 The second file to compare
107 * @return a negative value if the first file's extension
108 * is less than the second, zero if the extensions are the
109 * same and a positive value if the first files extension
110 * is greater than the second file.
111 */
112 @Override
113 public int compare(final File file1, final File file2) {
114 final String suffix1 = FilenameUtils.getExtension(file1.getName());
115 final String suffix2 = FilenameUtils.getExtension(file2.getName());
116 return ioCase.checkCompareTo(suffix1, suffix2);
117 }
118
119 /**
120 * String representation of this file comparator.
121 *
122 * @return String representation of this file comparator
123 */
124 @Override
125 public String toString() {
126 return super.toString() + "[ioCase=" + ioCase + "]";
127 }
128 }