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 * <p>
029 * Example of sorting a list of files/directories using the {@link #DIRECTORY_COMPARATOR} singleton instance:
030 * </p>
031 *
032 * <pre>
033 *       List&lt;File&gt; list = ...
034 *       ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_COMPARATOR).sort(list);
035 * </pre>
036 * <p>
037 * Example of doing a <em>reverse</em> sort of an array of files/directories using the {@link #DIRECTORY_REVERSE}
038 * singleton instance:
039 * </p>
040 *
041 * <pre>
042 *       File[] array = ...
043 *       ((AbstractFileComparator) DirectoryFileComparator.DIRECTORY_REVERSE).sort(array);
044 * </pre>
045 * <h2>Deprecating Serialization</h2>
046 * <p>
047 * <em>Serialization is deprecated and will be removed in 3.0.</em>
048 * </p>
049 *
050 * @since 2.0
051 */
052public class DirectoryFileComparator extends AbstractFileComparator implements Serializable {
053
054    private static final int TYPE_FILE = 2;
055
056    private static final int TYPE_DIRECTORY = 1;
057
058    private static final long serialVersionUID = 296132640160964395L;
059
060    /** Singleton default comparator instance */
061    public static final Comparator<File> DIRECTORY_COMPARATOR = new DirectoryFileComparator();
062
063    /** Singleton reverse default comparator instance */
064    public static final Comparator<File> DIRECTORY_REVERSE = new ReverseFileComparator(DIRECTORY_COMPARATOR);
065
066    /**
067     * Compares the two files using the {@link File#isDirectory()} method.
068     *
069     * @param file1 The first file to compare.
070     * @param file2 The second file to compare.
071     * @return the result of calling file1's {@link File#compareTo(File)} with file2 as the parameter.
072     */
073    @Override
074    public int compare(final File file1, final File file2) {
075        return getType(file1) - getType(file2);
076    }
077
078    /**
079     * Converts type to numeric value.
080     *
081     * @param file The file.
082     * @return 1 for directories and 2 for files.
083     */
084    private int getType(final File file) {
085        return file.isDirectory() ? TYPE_DIRECTORY : TYPE_FILE;
086    }
087}