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 two files using the {@link File#isDirectory()} method.
025     * <p>
026     * This comparator can be used to sort lists or arrays by directories and files.
027     * <p>
028     * Example of sorting a list of files/directories using the
029     * {@link #DIRECTORY_COMPARATOR} singleton instance:
030     * <pre>
031     *       List&lt;File&gt; list = ...
032     *       DirectoryFileComparator.DIRECTORY_COMPARATOR.sort(list);
033     * </pre>
034     * <p>
035     * Example of doing a <i>reverse</i> sort of an array of files/directories using the
036     * {@link #DIRECTORY_REVERSE} singleton instance:
037     * <pre>
038     *       File[] array = ...
039     *       DirectoryFileComparator.DIRECTORY_REVERSE.sort(array);
040     * </pre>
041     * <p>
042     *
043     * @version $Id: DirectoryFileComparator.java 1304052 2012-03-22 20:55:29Z ggregory $
044     * @since 2.0
045     */
046    public class DirectoryFileComparator extends AbstractFileComparator implements Serializable {
047    
048        /** Singleton default comparator instance */
049        public static final Comparator<File> DIRECTORY_COMPARATOR = new DirectoryFileComparator();
050    
051        /** Singleton reverse default comparator instance */
052        public static final Comparator<File> DIRECTORY_REVERSE = new ReverseComparator(DIRECTORY_COMPARATOR);
053    
054        /**
055         * Compare the two files using the {@link File#isDirectory()} method.
056         * 
057         * @param file1 The first file to compare
058         * @param file2 The second file to compare
059         * @return the result of calling file1's
060         * {@link File#compareTo(File)} with file2 as the parameter.
061         */
062        public int compare(File file1, File file2) {
063            return getType(file1) - getType(file2);
064        }
065    
066        /**
067         * Convert type to numeric value.
068         *
069         * @param file The file
070         * @return 1 for directories and 2 for files
071         */
072        private int getType(File file) {
073            if (file.isDirectory()) {
074                return 1;
075            } else {
076                return 2;
077            }
078        }
079    }