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 */
017package org.apache.commons.io.comparator;
018
019import java.io.File;
020import java.io.Serializable;
021import 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 *       ((AbstractFileComparator) 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 *       ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_REVERSE).sort(array);
040 * </pre>
041 * <p>
042 *
043 * @since 2.0
044 */
045public class DirectoryFileComparator extends AbstractFileComparator implements Serializable {
046
047    private static final int TYPE_FILE = 2;
048
049    private static final int TYPE_DIRECTORY = 1;
050
051    private static final long serialVersionUID = 296132640160964395L;
052
053    /** Singleton default comparator instance */
054    public static final Comparator<File> DIRECTORY_COMPARATOR = new DirectoryFileComparator();
055
056    /** Singleton reverse default comparator instance */
057    public static final Comparator<File> DIRECTORY_REVERSE = new ReverseFileComparator(DIRECTORY_COMPARATOR);
058
059    /**
060     * Compare the two files using the {@link File#isDirectory()} method.
061     *
062     * @param file1 The first file to compare
063     * @param file2 The second file to compare
064     * @return the result of calling file1's
065     * {@link File#compareTo(File)} with file2 as the parameter.
066     */
067    @Override
068    public int compare(final File file1, final File file2) {
069        return getType(file1) - getType(file2);
070    }
071
072    /**
073     * Convert type to numeric value.
074     *
075     * @param file The file
076     * @return 1 for directories and 2 for files
077     */
078    private int getType(final File file) {
079        return file.isDirectory() ? TYPE_DIRECTORY : TYPE_FILE;
080    }
081}