    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 *      https://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     * Construct a new instance.
    068     */
    069    public DirectoryFileComparator() {
    070        // empty
    071    }
    072
    073    /**
    074     * Compares the two files using the {@link File#isDirectory()} method.
    075     *
    076     * @param file1 The first file to compare.
    077     * @param file2 The second file to compare.
    078     * @return the result of calling file1's {@link File#compareTo(File)} with file2 as the parameter.
    079     */
    080    @Override
    081    public int compare(final File file1, final File file2) {
    082        return getType(file1) - getType(file2);
    083    }
    084
    085    /**
    086     * Converts type to numeric value.
    087     *
    088     * @param file The file.
    089     * @return 1 for directories and 2 for files.
    090     */
    091    private int getType(final File file) {
    092        return file.isDirectory() ? TYPE_DIRECTORY : TYPE_FILE;
    093    }
    094}