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      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 /**
     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  */
     48 public 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