    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 <i>hidden</i> 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 <i>visible</i> (i.e. 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 dir
    060 * Files.<b>walkFileTree</b>(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 dir tree
    067 * Files.<b>walkFileTree</b>(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 <i>hidden</i> filter */
    082    public static final IOFileFilter HIDDEN  = new HiddenFileFilter();
    083
    084    private static final long serialVersionUID = 8930842316112759062L;
    085
    086    /** Singleton instance of <i>visible</i> 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     *  <i>hidden</i>, 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     * @param file  the File to check
    110     *
    111     * @return {@code true} if the file is
    112     *  <i>hidden</i>, 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}