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 1.3
049     * @version $Id: HiddenFileFilter.java 1307462 2012-03-30 15:13:11Z ggregory $
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} if the file is
070         *  <i>hidden</i>, otherwise {@code false}.
071         */
072        @Override
073        public boolean accept(File file) {
074            return file.isHidden();
075        }
076        
077    }