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 */ 17 18 package libcore.io; 19 20 21 import java.io.File; 22 import java.util.ArrayList; 23 import java.util.Collections; 24 25 /** 26 * Implements the actual DeleteOnExit mechanism. Is registered as a shutdown 27 * hook in the Runtime, once it is actually being used. 28 */ 29 public class DeleteOnExit extends Thread { 30 31 /** 32 * Our singleton instance. 33 */ 34 private static DeleteOnExit instance; 35 36 /** 37 * Returns our singleton instance, creating it if necessary. 38 */ getInstance()39 public static synchronized DeleteOnExit getInstance() { 40 if (instance == null) { 41 instance = new DeleteOnExit(); 42 Runtime.getRuntime().addShutdownHook(instance); 43 } 44 45 return instance; 46 } 47 48 /** 49 * Our list of files scheduled for deletion. 50 */ 51 private final ArrayList<String> files = new ArrayList<String>(); 52 53 DeleteOnExit()54 private DeleteOnExit() { 55 } 56 57 /** 58 * Schedules a file for deletion. 59 * 60 * @param filename The file to delete. 61 */ addFile(String filename)62 public void addFile(String filename) { 63 synchronized (files) { 64 if (!files.contains(filename)) { 65 files.add(filename); 66 } 67 } 68 } 69 70 /** 71 * Does the actual work. Note we (a) first sort the files lexicographically 72 * and then (b) delete them in reverse order. This is to make sure files 73 * get deleted before their parent directories. 74 */ 75 @Override run()76 public void run() { 77 Collections.sort(files); 78 for (int i = files.size() - 1; i >= 0; i--) { 79 new File(files.get(i)).delete(); 80 } 81 } 82 } 83