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 */
17package org.apache.commons.io.comparator;
18
19import java.io.File;
20import java.io.Serializable;
21import java.util.Comparator;
22
23/**
24 * Compare the <b>last modified date/time</b> of two files for order
25 * (see {@link File#lastModified()}).
26 * <p>
27 * This comparator can be used to sort lists or arrays of files
28 * by their last modified date/time.
29 * <p>
30 * Example of sorting a list of files using the
31 * {@link #LASTMODIFIED_COMPARATOR} singleton instance:
32 * <pre>
33 *       List&lt;File&gt; list = ...
34 *       Collections.sort(list, LastModifiedFileComparator.LASTMODIFIED_COMPARATOR);
35 * </pre>
36 * <p>
37 * Example of doing a <i>reverse</i> sort of an array of files using the
38 * {@link #LASTMODIFIED_REVERSE} singleton instance:
39 * <pre>
40 *       File[] array = ...
41 *       Arrays.sort(array, LastModifiedFileComparator.LASTMODIFIED_REVERSE);
42 * </pre>
43 * <p>
44 *
45 * @version $Revision: 609243 $ $Date: 2008-01-06 00:30:42 +0000 (Sun, 06 Jan 2008) $
46 * @since Commons IO 1.4
47 */
48public class LastModifiedFileComparator implements Comparator<File>, Serializable {
49
50    /** Last modified comparator instance */
51    public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
52
53    /** Reverse last modified comparator instance */
54    public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseComparator<File>(LASTMODIFIED_COMPARATOR);
55
56    /**
57     * Compare the last the last modified date/time of two files.
58     *
59     * @param obj1 The first file to compare
60     * @param obj2 The second file to compare
61     * @return a negative value if the first file's lastmodified date/time
62     * is less than the second, zero if the lastmodified date/time are the
63     * same and a positive value if the first files lastmodified date/time
64     * is greater than the second file.
65     *
66     */
67    public int compare(File file1, File file2) {
68        long result = file1.lastModified() - file2.lastModified();
69        if (result < 0) {
70            return -1;
71        } else if (result > 0) {
72            return 1;
73        } else {
74            return 0;
75        }
76    }
77}
78