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.FileUtils;
24
25 /**
26 * Compare the <b>last modified date/time</b> of two files for order
27 * (see {@link FileUtils#lastModifiedUnchecked(File)}).
28 * <p>
29 * This comparator can be used to sort lists or arrays of files
30 * by their last modified date/time.
31 * </p>
32 * <p>
33 * Example of sorting a list of files using the
34 * {@link #LASTMODIFIED_COMPARATOR} singleton instance:
35 * </p>
36 * <pre>
37 * List<File> list = ...
38 * ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_COMPARATOR).sort(list);
39 * </pre>
40 * <p>
41 * Example of doing a <i>reverse</i> sort of an array of files using the
42 * {@link #LASTMODIFIED_REVERSE} singleton instance:
43 * </p>
44 * <pre>
45 * File[] array = ...
46 * ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_REVERSE).sort(array);
47 * </pre>
48 * <h2>Deprecating Serialization</h2>
49 * <p>
50 * <em>Serialization is deprecated and will be removed in 3.0.</em>
51 * </p>
52 *
53 * @since 1.4
54 */
55 public class LastModifiedFileComparator extends AbstractFileComparator implements Serializable {
56
57 private static final long serialVersionUID = 7372168004395734046L;
58
59 /** Last modified comparator instance. */
60 public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
61
62 /** Reverse last modified comparator instance. */
63 public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseFileComparator(LASTMODIFIED_COMPARATOR);
64
65 /**
66 * Compares the last modified date/time of two files.
67 *
68 * @param file1 The first file to compare.
69 * @param file2 The second file to compare.
70 * @return a negative value if the first file's last modified date/time is less than the second, zero if the last
71 * modified date/time are the same and a positive value if the first files last modified date/time is
72 * greater than the second file.
73 */
74 @Override
75 public int compare(final File file1, final File file2) {
76 final long result = FileUtils.lastModifiedUnchecked(file1) - FileUtils.lastModifiedUnchecked(file2);
77 if (result < 0) {
78 return -1;
79 }
80 if (result > 0) {
81 return 1;
82 }
83 return 0;
84 }
85 }