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    import org.apache.commons.io.IOCase;
024    
025    /**
026     * Compare the <b>names</b> of two files for order (see {@link File#getName()}).
027     * <p>
028     * This comparator can be used to sort lists or arrays of files
029     * by their name either in a case-sensitive, case-insensitive or
030     * system dependant case sensitive way. A number of singleton instances
031     * are provided for the various case sensitivity options (using {@link IOCase})
032     * and the reverse of those options.
033     * <p>
034     * Example of a <i>case-sensitive</i> file name sort using the
035     * {@link #NAME_COMPARATOR} singleton instance:
036     * <pre>
037     *       List&lt;File&gt; list = ...
038     *       NameFileComparator.NAME_COMPARATOR.sort(list);
039     * </pre>
040     * <p>
041     * Example of a <i>reverse case-insensitive</i> file name sort using the
042     * {@link #NAME_INSENSITIVE_REVERSE} singleton instance:
043     * <pre>
044     *       File[] array = ...
045     *       NameFileComparator.NAME_INSENSITIVE_REVERSE.sort(array);
046     * </pre>
047     * <p>
048     *
049     * @version $Id: NameFileComparator.java 1304052 2012-03-22 20:55:29Z ggregory $
050     * @since 1.4
051     */
052    public class NameFileComparator extends AbstractFileComparator implements Serializable {
053    
054        /** Case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
055        public static final Comparator<File> NAME_COMPARATOR = new NameFileComparator();
056    
057        /** Reverse case-sensitive name comparator instance (see {@link IOCase#SENSITIVE}) */
058        public static final Comparator<File> NAME_REVERSE = new ReverseComparator(NAME_COMPARATOR);
059    
060        /** Case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
061        public static final Comparator<File> NAME_INSENSITIVE_COMPARATOR = new NameFileComparator(IOCase.INSENSITIVE);
062    
063        /** Reverse case-insensitive name comparator instance (see {@link IOCase#INSENSITIVE}) */
064        public static final Comparator<File> NAME_INSENSITIVE_REVERSE = new ReverseComparator(NAME_INSENSITIVE_COMPARATOR);
065    
066        /** System sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
067        public static final Comparator<File> NAME_SYSTEM_COMPARATOR = new NameFileComparator(IOCase.SYSTEM);
068    
069        /** Reverse system sensitive name comparator instance (see {@link IOCase#SYSTEM}) */
070        public static final Comparator<File> NAME_SYSTEM_REVERSE = new ReverseComparator(NAME_SYSTEM_COMPARATOR);
071    
072        /** Whether the comparison is case sensitive. */
073        private final IOCase caseSensitivity;
074    
075        /**
076         * Construct a case sensitive file name comparator instance.
077         */
078        public NameFileComparator() {
079            this.caseSensitivity = IOCase.SENSITIVE;
080        }
081    
082        /**
083         * Construct a file name comparator instance with the specified case-sensitivity.
084         *
085         * @param caseSensitivity  how to handle case sensitivity, null means case-sensitive
086         */
087        public NameFileComparator(IOCase caseSensitivity) {
088            this.caseSensitivity = caseSensitivity == null ? IOCase.SENSITIVE : caseSensitivity;
089        }
090    
091        /**
092         * Compare the names of two files with the specified case sensitivity.
093         * 
094         * @param file1 The first file to compare
095         * @param file2 The second file to compare
096         * @return a negative value if the first file's name
097         * is less than the second, zero if the names are the
098         * same and a positive value if the first files name
099         * 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        /**
106         * String representation of this file comparator.
107         *
108         * @return String representation of this file comparator
109         */
110        @Override
111        public String toString() {
112            return super.toString() + "[caseSensitivity=" + caseSensitivity + "]";
113        }
114    }