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     */
017    package org.apache.commons.io.comparator;
018    
019    import java.io.File;
020    import java.io.Serializable;
021    import 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     *       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     *       LastModifiedFileComparator.LASTMODIFIED_REVERSE.sort(array);
042     * </pre>
043     * <p>
044     *
045     * @version $Id: LastModifiedFileComparator.java 1304052 2012-03-22 20:55:29Z ggregory $
046     * @since 1.4
047     */
048    public class LastModifiedFileComparator extends AbstractFileComparator implements Serializable {
049    
050        /** Last modified comparator instance */
051        public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
052    
053        /** Reverse last modified comparator instance */
054        public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseComparator(LASTMODIFIED_COMPARATOR);
055    
056        /**
057         * Compare the last the last modified date/time of two files.
058         * 
059         * @param file1 The first file to compare
060         * @param file2 The second file to compare
061         * @return a negative value if the first file's lastmodified date/time
062         * is less than the second, zero if the lastmodified date/time are the
063         * same and a positive value if the first files lastmodified date/time
064         * is greater than the second file.
065         * 
066         */
067        public int compare(File file1, File file2) {
068            long result = file1.lastModified() - file2.lastModified();
069            if (result < 0) {
070                return -1;
071            } else if (result > 0) {
072                return 1;
073            } else {
074                return 0;
075            }
076        }
077    }