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;
021import java.nio.file.FileVisitResult;
022import java.nio.file.Files;
023import java.nio.file.Path;
024import java.nio.file.attribute.BasicFileAttributes;
025
026/**
027 * This filter accepts {@link File}s that are directories.
028 * <p>
029 * For example, here is how to print out a list of the current directory's subdirectories:
030 * </p>
031 * <h2>Using Classic IO</h2>
032 *
033 * <pre>
034 * File dir = FileUtils.current();
035 * String[] files = dir.list(DirectoryFileFilter.INSTANCE);
036 * for (String file : files) {
037 *     System.out.println(file);
038 * }
039 * </pre>
040 *
041 * <h2>Using NIO</h2>
042 *
043 * <pre>
044 * final Path dir = PathUtils.current();
045 * final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(DirectoryFileFilter.INSTANCE);
046 * //
047 * // Walk one dir
048 * Files.<b>walkFileTree</b>(dir, Collections.emptySet(), 1, visitor);
049 * System.out.println(visitor.getPathCounters());
050 * System.out.println(visitor.getFileList());
051 * //
052 * visitor.getPathCounters().reset();
053 * //
054 * // Walk dir tree
055 * Files.<b>walkFileTree</b>(dir, visitor);
056 * System.out.println(visitor.getPathCounters());
057 * System.out.println(visitor.getDirList());
058 * System.out.println(visitor.getFileList());
059 * </pre>
060 * <h2>Deprecating Serialization</h2>
061 * <p>
062 * <em>Serialization is deprecated and will be removed in 3.0.</em>
063 * </p>
064 *
065 * @since 1.0
066 * @see FileFilterUtils#directoryFileFilter()
067 */
068public class DirectoryFileFilter extends AbstractFileFilter implements Serializable {
069
070    /**
071     * Singleton instance of directory filter.
072     *
073     * @since 1.3
074     */
075    public static final IOFileFilter DIRECTORY = new DirectoryFileFilter();
076
077    /**
078     * Singleton instance of directory filter. Please use the identical DirectoryFileFilter.DIRECTORY constant. The new
079     * name is more JDK 1.5 friendly as it doesn't clash with other values when using static imports.
080     */
081    public static final IOFileFilter INSTANCE = DIRECTORY;
082
083    private static final long serialVersionUID = -5148237843784525732L;
084
085    /**
086     * Restrictive constructor.
087     */
088    protected DirectoryFileFilter() {
089        // empty.
090    }
091
092    /**
093     * Checks to see if the file is a directory.
094     *
095     * @param file the File to check
096     * @return true if the file is a directory
097     */
098    @Override
099    public boolean accept(final File file) {
100        return file != null && file.isDirectory();
101    }
102
103    /**
104     * Checks to see if the file is a directory.
105     * @param file the File to check
106     *
107     * @return true if the file is a directory
108     * @since 2.9.0
109     */
110    @Override
111    public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
112        return toFileVisitResult(file != null && Files.isDirectory(file));
113    }
114
115}