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.vfs2.filter; 018 019import java.io.Serializable; 020 021import org.apache.commons.vfs2.FileContent; 022import org.apache.commons.vfs2.FileFilter; 023import org.apache.commons.vfs2.FileObject; 024import org.apache.commons.vfs2.FileSelectInfo; 025import org.apache.commons.vfs2.FileSystemException; 026import org.apache.commons.vfs2.FileType; 027 028/** 029 * This filter accepts files or directories that are empty. 030 * <p> 031 * If the {@code File} is a directory it checks that it contains no files. 032 * </p> 033 * <p> 034 * Example, showing how to print out a list of the current directory's empty files/directories: 035 * </p> 036 * 037 * <pre> 038 * FileSystemManager fsManager = VFS.getManager(); 039 * FileObject dir = fsManager.toFileObject(new File(".")); 040 * FileObject[] files = dir.findFiles(new FileFilterSelector(EmptyFileFilter.EMPTY)); 041 * for (int i = 0; i < files.length; i++) { 042 * System.out.println(files[i]); 043 * } 044 * </pre> 045 * 046 * <p> 047 * Example, showing how to print out a list of the current directory's non-empty files/directories: 048 * </p> 049 * 050 * <pre> 051 * FileSystemManager fsManager = VFS.getManager(); 052 * FileObject dir = fsManager.toFileObject(new File(".")); 053 * FileObject[] files = dir.findFiles(new FileFilterSelector(EmptyFileFilter.NOT_EMPTY)); 054 * for (int i = 0; i < files.length; i++) { 055 * System.out.println(files[i]); 056 * } 057 * </pre> 058 * 059 * @author This code was originally ported from Apache Commons IO File Filter 060 * @see "https://commons.apache.org/proper/commons-io/" 061 * @since 2.4 062 */ 063public class EmptyFileFilter implements FileFilter, Serializable { 064 065 /** Singleton instance of <em>empty</em> filter. */ 066 public static final FileFilter EMPTY = new EmptyFileFilter(); 067 068 /** Singleton instance of <em>not-empty</em> filter. */ 069 public static final FileFilter NOT_EMPTY = new NotFileFilter(EMPTY); 070 071 private static final long serialVersionUID = 1L; 072 073 /** 074 * Restrictive constructor. 075 */ 076 protected EmptyFileFilter() { 077 } 078 079 /** 080 * Checks to see if the file is empty. A non-existing file is also considered empty. 081 * 082 * @param fileSelectInfo the file or directory to check 083 * @return {@code true} if the file or directory is <em>empty</em>, otherwise {@code false}. 084 * @throws FileSystemException Thrown for file system errors. 085 */ 086 @Override 087 public boolean accept(final FileSelectInfo fileSelectInfo) throws FileSystemException { 088 try (FileObject file = fileSelectInfo.getFile()) { 089 if (!file.exists()) { 090 return true; 091 } 092 if (file.getType() == FileType.FOLDER) { 093 final FileObject[] files = file.getChildren(); 094 return files == null || files.length == 0; 095 } 096 try (FileContent content = file.getContent()) { 097 return content.isEmpty(); 098 } 099 } 100 } 101 102}