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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 import org.apache.commons.io.IOCase;
     24 
     25 /**
     26  * Compare the <b>names</b> of two files for order (see {@link File#getName()}).
     27  * <p>
     28  * This comparator can be used to sort lists or arrays of files
     29  * by their name either in a case-sensitive, case-insensitive or
     30  * system dependant case sensitive way. A number of singleton instances
     31  * are provided for the various case sensitivity options (using {@link IOCase})
     32  * and the reverse of those options.
     33  * <p>
     34  * Example of a <i>case-sensitive</i> file name sort using the
     35  * {@link #NAME_COMPARATOR} singleton instance:
     36  * <pre>
     37  *       List&lt;File&gt; list = ...
     38  *       Collections.sort(list, NameFileComparator.NAME_COMPARATOR);
     39  * </pre>
     40  * <p>
     41  * Example of a <i>reverse case-insensitive</i> file name sort using the
     42  * {@link #NAME_INSENSITIVE_REVERSE} singleton instance:
     43  * <pre>
     44  *       File[] array = ...
     45  *       Arrays.sort(array, NameFileComparator.NAME_INSENSITIVE_REVERSE);
     46  * </pre>
     47  * <p>
     48  *
     49  * @version $Revision: 609243 $ $Date: 2008-01-06 00:30:42 +0000 (Sun, 06 Jan 2008) $
     50  * @since Commons IO 1.4
     51  */
     52 public class NameFileComparator implements Comparator<File>, Serializable {
     53 
     54     /** Case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
     55     public static final Comparator<File> NAME_COMPARATOR = new NameFileComparator();
     56 
     57     /** Reverse case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
     58     public static final Comparator<File> NAME_REVERSE = new ReverseComparator<File>(NAME_COMPARATOR);
     59 
     60     /** Case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
     61     public static final Comparator<File> NAME_INSENSITIVE_COMPARATOR = new NameFileComparator(IOCase.INSENSITIVE);
     62 
     63     /** Reverse case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
     64     public static final Comparator<File> NAME_INSENSITIVE_REVERSE = new ReverseComparator<File>(NAME_INSENSITIVE_COMPARATOR);
     65 
     66     /** System sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
     67     public static final Comparator<File> NAME_SYSTEM_COMPARATOR = new NameFileComparator(IOCase.SYSTEM);
     68 
     69     /** Reverse system sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
     70     public static final Comparator<File> NAME_SYSTEM_REVERSE = new ReverseComparator<File>(NAME_SYSTEM_COMPARATOR);
     71 
     72     /** Whether the comparison is case sensitive. */
     73     private final IOCase caseSensitivity;
     74 
     75     /**
     76      * Construct a case sensitive file name comparator instance.
     77      */
     78     public NameFileComparator() {
     79         this.caseSensitivity = IOCase.SENSITIVE;
     80     }
     81 
     82     /**
     83      * Construct a file name comparator instance with the specified case-sensitivity.
     84      *
     85      * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
     86      */
     87     public NameFileComparator(IOCase caseSensitivity) {
     88         this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity;
     89     }
     90 
     91     /**
     92      * Compare the names of two files with the specified case sensitivity.
     93      *
     94      * @param obj1 The first file to compare
     95      * @param obj2 The second file to compare
     96      * @return a negative value if the first file's name
     97      * is less than the second, zero if the names are the
     98      * same and a positive value if the first files name
     99      * is greater than the second file.
    100      */
    101     public int compare(File file1, File file2) {
    102         return caseSensitivity.checkCompareTo(file1.getName(), file2.getName());
    103     }
    104 }
    105