001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.comparator;
018
019import java.io.File;
020import java.io.Serializable;
021import java.util.Comparator;
022
023/**
024 * Compare the <b>last modified date/time</b> of two files for order 
025 * (see {@link File#lastModified()}).
026 * <p>
027 * This comparator can be used to sort lists or arrays of files
028 * by their last modified date/time.
029 * <p>
030 * Example of sorting a list of files using the
031 * {@link #LASTMODIFIED_COMPARATOR} singleton instance:
032 * <pre>
033 *       List&lt;File&gt; list = ...
034 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_COMPARATOR).sort(list);
035 * </pre>
036 * <p>
037 * Example of doing a <i>reverse</i> sort of an array of files using the
038 * {@link #LASTMODIFIED_REVERSE} singleton instance:
039 * <pre>
040 *       File[] array = ...
041 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_REVERSE).sort(array);
042 * </pre>
043 * <p>
044 *
045 * @version $Id: LastModifiedFileComparator.java 1642757 2014-12-01 21:09:30Z sebb $
046 * @since 1.4
047 */
048public class LastModifiedFileComparator extends AbstractFileComparator implements Serializable {
049
050    private static final long serialVersionUID = 7372168004395734046L;
051
052    /** Last modified comparator instance */
053    public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
054
055    /** Reverse last modified comparator instance */
056    public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseComparator(LASTMODIFIED_COMPARATOR);
057
058    /**
059     * Compare the last the last modified date/time of two files.
060     * 
061     * @param file1 The first file to compare
062     * @param file2 The second file to compare
063     * @return a negative value if the first file's lastmodified date/time
064     * is less than the second, zero if the lastmodified date/time are the
065     * same and a positive value if the first files lastmodified date/time
066     * is greater than the second file.
067     * 
068     */
069    public int compare(final File file1, final File file2) {
070        final long result = file1.lastModified() - file2.lastModified();
071        if (result < 0) {
072            return -1;
073        } else if (result > 0) {
074            return 1;
075        } else {
076            return 0;
077        }
078    }
079}