    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 $Revision$ $Date$
    044     * @since Commons IO 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    }