    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 *
    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 constructor.
    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}