    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     */
    017    package org.apache.commons.io.filefilter;
    018
    019    import java.io.File;
    020    import java.io.Serializable;
    021
    022    /**
    023     * This filter accepts <code>File</code>s that are hidden.
    024     * <p>
    025     * Example, showing how to print out a list of the
    026     * current directory's <i>hidden</i> files:
    027     *
    028     * <pre>
    029     * File dir = new File(".");
    030     * String[] files = dir.list( HiddenFileFilter.HIDDEN );
    031     * for ( int i = 0; i &lt; files.length; i++ ) {
    032     *     System.out.println(files[i]);
    033     * }
    034     * </pre>
    035     *
    036     * <p>
    037     * Example, showing how to print out a list of the
    038     * current directory's <i>visible</i> (i.e. not hidden) files:
    039     *
    040     * <pre>
    041     * File dir = new File(".");
    042     * String[] files = dir.list( HiddenFileFilter.VISIBLE );
    043     * for ( int i = 0; i &lt; files.length; i++ ) {
    044     *     System.out.println(files[i]);
    045     * }
    046     * </pre>
    047     *
    048     * @since Commons IO 1.3
    049     * @version $Revision: 659817 $
    050     */
    051    public class HiddenFileFilter extends AbstractFileFilter implements Serializable {
    052
    053        /** Singleton instance of <i>hidden</i> filter */
    054        public static final IOFileFilter HIDDEN  = new HiddenFileFilter();
    055
    056        /** Singleton instance of <i>visible</i> filter */
    057        public static final IOFileFilter VISIBLE = new NotFileFilter(HIDDEN);
    058
    059        /**
    060         * Restrictive consructor.
    061         */
    062        protected HiddenFileFilter() {
    063        }
    064
    065        /**
    066         * Checks to see if the file is hidden.
    067         *
    068         * @param file  the File to check
    069         * @return <code>true</code> if the file is
    070         *  <i>hidden</i>, otherwise <code>false</code>.
    071         */
    072        @Override
    073        public boolean accept(File file) {
    074            return file.isHidden();
    075        }
    076
    077    }