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.filefilter;
018
019import java.io.File;
020import java.io.Serializable;
021
022/**
023 * This filter accepts <code>File</code>s that are directories.
024 * <p>
025 * For example, here is how to print out a list of the 
026 * current directory's subdirectories:
027 *
028 * <pre>
029 * File dir = new File(".");
030 * String[] files = dir.list( DirectoryFileFilter.INSTANCE );
031 * for ( int i = 0; i &lt; files.length; i++ ) {
032 *     System.out.println(files[i]);
033 * }
034 * </pre>
035 *
036 * @since 1.0
037 * @version $Id: DirectoryFileFilter.java 1642757 2014-12-01 21:09:30Z sebb $
038 *
039 * @see FileFilterUtils#directoryFileFilter()
040 */
041public class DirectoryFileFilter extends AbstractFileFilter implements Serializable {
042
043    private static final long serialVersionUID = -5148237843784525732L;
044    /**
045     * Singleton instance of directory filter.
046     * @since 1.3
047     */
048    public static final IOFileFilter DIRECTORY = new DirectoryFileFilter();
049    /**
050     * Singleton instance of directory filter.
051     * Please use the identical DirectoryFileFilter.DIRECTORY constant.
052     * The new name is more JDK 1.5 friendly as it doesn't clash with other
053     * values when using static imports.
054     */
055    public static final IOFileFilter INSTANCE = DIRECTORY;
056
057    /**
058     * Restrictive consructor.
059     */
060    protected DirectoryFileFilter() {
061    }
062
063    /**
064     * Checks to see if the file is a directory.
065     *
066     * @param file  the File to check
067     * @return true if the file is a directory
068     */
069    @Override
070    public boolean accept(final File file) {
071        return file.isDirectory();
072    }
073
074}