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 */ 017package org.apache.commons.io.filefilter; 018 019import java.io.File; 020import java.io.IOException; 021import java.io.Serializable; 022import java.nio.file.FileVisitResult; 023import java.nio.file.Files; 024import java.nio.file.Path; 025import java.nio.file.attribute.BasicFileAttributes; 026import java.util.stream.Stream; 027 028import org.apache.commons.io.IOUtils; 029 030/** 031 * This filter accepts files or directories that are empty. 032 * <p> 033 * If the {@code File} is a directory it checks that it contains no files. 034 * </p> 035 * <p> 036 * Example, showing how to print out a list of the current directory's empty files/directories: 037 * </p> 038 * <h2>Using Classic IO</h2> 039 * <pre> 040 * File dir = new File("."); 041 * String[] files = dir.list(EmptyFileFilter.EMPTY); 042 * for (String file : files) { 043 * System.out.println(file); 044 * } 045 * </pre> 046 * 047 * <p> 048 * Example, showing how to print out a list of the current directory's non-empty files/directories: 049 * </p> 050 * 051 * <pre> 052 * File dir = new File("."); 053 * String[] files = dir.list(EmptyFileFilter.NOT_EMPTY); 054 * for (String file : files) { 055 * System.out.println(file); 056 * } 057 * </pre> 058 * 059 * <h2>Using NIO</h2> 060 * <pre> 061 * final Path dir = Paths.get(""); 062 * final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(EmptyFileFilter.EMPTY); 063 * // 064 * // Walk one dir 065 * Files.<b>walkFileTree</b>(dir, Collections.emptySet(), 1, visitor); 066 * System.out.println(visitor.getPathCounters()); 067 * System.out.println(visitor.getFileList()); 068 * // 069 * visitor.getPathCounters().reset(); 070 * // 071 * // Walk dir tree 072 * Files.<b>walkFileTree</b>(dir, visitor); 073 * System.out.println(visitor.getPathCounters()); 074 * System.out.println(visitor.getDirList()); 075 * System.out.println(visitor.getFileList()); 076 * </pre> 077 * 078 * @since 1.3 079 */ 080public class EmptyFileFilter extends AbstractFileFilter implements Serializable { 081 082 /** Singleton instance of <i>empty</i> filter */ 083 public static final IOFileFilter EMPTY = new EmptyFileFilter(); 084 085 /** Singleton instance of <i>not-empty</i> filter */ 086 public static final IOFileFilter NOT_EMPTY = EMPTY.negate(); 087 088 private static final long serialVersionUID = 3631422087512832211L; 089 090 /** 091 * Restrictive constructor. 092 */ 093 protected EmptyFileFilter() { 094 } 095 096 /** 097 * Checks to see if the file is empty. 098 * 099 * @param file the file or directory to check 100 * @return {@code true} if the file or directory is <i>empty</i>, otherwise {@code false}. 101 */ 102 @Override 103 public boolean accept(final File file) { 104 if (file.isDirectory()) { 105 final File[] files = file.listFiles(); 106 return IOUtils.length(files) == 0; 107 } 108 return file.length() == 0; 109 } 110 111 /** 112 * Checks to see if the file is empty. 113 * @param file the file or directory to check 114 * 115 * @return {@code true} if the file or directory is <i>empty</i>, otherwise {@code false}. 116 * @since 2.9.0 117 */ 118 @Override 119 public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) { 120 try { 121 if (Files.isDirectory(file)) { 122 try (Stream<Path> stream = Files.list(file)) { 123 return toFileVisitResult(!stream.findFirst().isPresent(), file); 124 } 125 } 126 return toFileVisitResult(Files.size(file) == 0, file); 127 } catch (final IOException e) { 128 return handle(e); 129 } 130 } 131 132}