1/* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17package org.apache.commons.io.filefilter; 18 19import java.io.File; 20import java.io.Serializable; 21 22/** 23 * This filter accepts files or directories that are empty. 24 * <p> 25 * If the <code>File</code> is a directory it checks that 26 * it contains no files. 27 * <p> 28 * Example, showing how to print out a list of the 29 * current directory's empty files/directories: 30 * 31 * <pre> 32 * File dir = new File("."); 33 * String[] files = dir.list( EmptyFileFilter.EMPTY ); 34 * for ( int i = 0; i < files.length; i++ ) { 35 * System.out.println(files[i]); 36 * } 37 * </pre> 38 * 39 * <p> 40 * Example, showing how to print out a list of the 41 * current directory's non-empty files/directories: 42 * 43 * <pre> 44 * File dir = new File("."); 45 * String[] files = dir.list( EmptyFileFilter.NOT_EMPTY ); 46 * for ( int i = 0; i < files.length; i++ ) { 47 * System.out.println(files[i]); 48 * } 49 * </pre> 50 * 51 * @since Commons IO 1.3 52 * @version $Revision: 587916 $ 53 */ 54public class EmptyFileFilter extends AbstractFileFilter implements Serializable { 55 56 /** Singleton instance of <i>empty</i> filter */ 57 public static final IOFileFilter EMPTY = new EmptyFileFilter(); 58 59 /** Singleton instance of <i>not-empty</i> filter */ 60 public static final IOFileFilter NOT_EMPTY = new NotFileFilter(EMPTY); 61 62 /** 63 * Restrictive consructor. 64 */ 65 protected EmptyFileFilter() { 66 } 67 68 /** 69 * Checks to see if the file is empty. 70 * 71 * @param file the file or directory to check 72 * @return <code>true</code> if the file or directory 73 * is <i>empty</i>, otherwise <code>false</code>. 74 */ 75 public boolean accept(File file) { 76 if (file.isDirectory()) { 77 File[] files = file.listFiles(); 78 return (files == null || files.length == 0); 79 } else { 80 return (file.length() == 0); 81 } 82 } 83 84} 85