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 }