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 < 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 < 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 }