    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 files or directories that are empty.
    024     * <p>
    025     * If the <code>File</code> is a directory it checks that
    026     * it contains no files.
    027     * <p>
    028     * Example, showing how to print out a list of the
    029     * current directory's empty files/directories:
    030     *
    031     * <pre>
    032     * File dir = new File(".");
    033     * String[] files = dir.list( EmptyFileFilter.EMPTY );
    034     * for ( int i = 0; i &lt; files.length; i++ ) {
    035     *     System.out.println(files[i]);
    036     * }
    037     * </pre>
    038     *
    039     * <p>
    040     * Example, showing how to print out a list of the
    041     * current directory's non-empty files/directories:
    042     *
    043     * <pre>
    044     * File dir = new File(".");
    045     * String[] files = dir.list( EmptyFileFilter.NOT_EMPTY );
    046     * for ( int i = 0; i &lt; files.length; i++ ) {
    047     *     System.out.println(files[i]);
    048     * }
    049     * </pre>
    050     *
    051     * @since Commons IO 1.3
    052     * @version $Revision: 659817 $
    053     */
    054    public class EmptyFileFilter extends AbstractFileFilter implements Serializable {
    055
    056        /** Singleton instance of <i>empty</i> filter */
    057        public static final IOFileFilter EMPTY = new EmptyFileFilter();
    058
    059        /** Singleton instance of <i>not-empty</i> filter */
    060        public static final IOFileFilter NOT_EMPTY = new NotFileFilter(EMPTY);
    061
    062        /**
    063         * Restrictive consructor.
    064         */
    065        protected EmptyFileFilter() {
    066        }
    067
    068        /**
    069         * Checks to see if the file is empty.
    070         *
    071         * @param file  the file or directory to check
    072         * @return <code>true</code> if the file or directory
    073         *  is <i>empty</i>, otherwise <code>false</code>.
    074         */
    075        @Override
    076        public boolean accept(File file) {
    077            if (file.isDirectory()) {
    078                File[] files = file.listFiles();
    079                return (files == null || files.length == 0);
    080            } else {
    081                return (file.length() == 0);
    082            }
    083        }
    084
    085    }