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 hidden.
028 * <p>
029 * Example, showing how to print out a list of the
030 * current directory's <em>hidden</em> files:
031 * </p>
032 * <h2>Using Classic IO</h2>
033 * <pre>
034 * File dir = FileUtils.current();
035 * String[] files = dir.list(HiddenFileFilter.HIDDEN);
036 * for (String file : files) {
037 *     System.out.println(file);
038 * }
039 * </pre>
040 *
041 * <p>
042 * Example, showing how to print out a list of the
043 * current directory's <em>visible</em> (not hidden) files:
044 * </p>
045 *
046 * <pre>
047 * File dir = FileUtils.current();
048 * String[] files = dir.list(HiddenFileFilter.VISIBLE);
049 * for (String file : files) {
050 *     System.out.println(file);
051 * }
052 * </pre>
053 *
054 * <h2>Using NIO</h2>
055 * <pre>
056 * final Path dir = PathUtils.current();
057 * final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(HiddenFileFilter.HIDDEN);
058 * //
059 * // Walk one directory
060 * Files.<strong>walkFileTree</strong>(dir, Collections.emptySet(), 1, visitor);
061 * System.out.println(visitor.getPathCounters());
062 * System.out.println(visitor.getFileList());
063 * //
064 * visitor.getPathCounters().reset();
065 * //
066 * // Walk directory tree
067 * Files.<strong>walkFileTree</strong>(dir, visitor);
068 * System.out.println(visitor.getPathCounters());
069 * System.out.println(visitor.getDirList());
070 * System.out.println(visitor.getFileList());
071 * </pre>
072 * <h2>Deprecating Serialization</h2>
073 * <p>
074 * <em>Serialization is deprecated and will be removed in 3.0.</em>
075 * </p>
076 *
077 * @since 1.3
078 */
079public class HiddenFileFilter extends AbstractFileFilter implements Serializable {
080
081    /** Singleton instance of <em>hidden</em> filter */
082    public static final IOFileFilter HIDDEN  = new HiddenFileFilter();
083
084    private static final long serialVersionUID = 8930842316112759062L;
085
086    /** Singleton instance of <em>visible</em> filter */
087    public static final IOFileFilter VISIBLE = HIDDEN.negate();
088
089    /**
090     * Restrictive constructor.
091     */
092    protected HiddenFileFilter() {
093    }
094
095    /**
096     * Checks to see if the file is hidden.
097     *
098     * @param file  the File to check
099     * @return {@code true} if the file is
100     *  <em>hidden</em>, otherwise {@code false}.
101     */
102    @Override
103    public boolean accept(final File file) {
104        return file == null || file.isHidden();
105    }
106
107    /**
108     * Checks to see if the file is hidden.
109     *
110     * @param file       the File to check
111     * @param attributes the path's basic attributes (may be null).
112     * @return {@code true} if the file is <em>hidden</em>, otherwise {@code false}.
113     * @since 2.9.0
114     */
115    @Override
116    public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
117        return get(() -> toFileVisitResult(file == null || Files.isHidden(file)));
118    }
119
120}