    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 *      https://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
    023import org.apache.commons.io.FileUtils;
    024
    025/**
    026 * Compare the <strong>last modified date/time</strong> of two files for order
    027 * (see {@link FileUtils#lastModifiedUnchecked(File)}).
    028 * <p>
    029 * This comparator can be used to sort lists or arrays of files
    030 * by their last modified date/time.
    031 * </p>
    032 * <p>
    033 * Example of sorting a list of files using the
    034 * {@link #LASTMODIFIED_COMPARATOR} singleton instance:
    035 * </p>
    036 * <pre>
    037 *       List&lt;File&gt; list = ...
    038 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_COMPARATOR).sort(list);
    039 * </pre>
    040 * <p>
    041 * Example of doing a <em>reverse</em> sort of an array of files using the
    042 * {@link #LASTMODIFIED_REVERSE} singleton instance:
    043 * </p>
    044 * <pre>
    045 *       File[] array = ...
    046 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_REVERSE).sort(array);
    047 * </pre>
    048 * <h2>Deprecating Serialization</h2>
    049 * <p>
    050 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    051 * </p>
    052 *
    053 * @since 1.4
    054 */
    055public class LastModifiedFileComparator extends AbstractFileComparator implements Serializable {
    056
    057    private static final long serialVersionUID = 7372168004395734046L;
    058
    059    /** Last modified comparator instance. */
    060    public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
    061
    062    /** Reverse last modified comparator instance. */
    063    public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseFileComparator(LASTMODIFIED_COMPARATOR);
    064
    065    /**
    066     * Construct a new instance.
    067     */
    068    public LastModifiedFileComparator() {
    069        // empty
    070    }
    071
    072    /**
    073     * Compares the last modified date/time of two files.
    074     *
    075     * @param file1 The first file to compare.
    076     * @param file2 The second file to compare.
    077     * @return a negative value if the first file's last modified date/time is less than the second, zero if the last
    078     *         modified date/time are the same and a positive value if the first files last modified date/time is
    079     *         greater than the second file.
    080     */
    081    @Override
    082    public int compare(final File file1, final File file2) {
    083        final long result = FileUtils.lastModifiedUnchecked(file1) - FileUtils.lastModifiedUnchecked(file2);
    084        if (result < 0) {
    085            return -1;
    086        }
    087        if (result > 0) {
    088            return 1;
    089        }
    090        return 0;
    091    }
    092}