1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 import java.lang.ref.WeakReference; 18 import java.util.ArrayList; 19 import java.util.List; 20 21 /** 22 * Some finalizer tests. 23 * 24 * This only works if System.runFinalization() causes finalizers to run 25 * immediately or very soon. 26 */ 27 public class Main { 28 private static void snooze(int ms) { 29 try { 30 Thread.sleep(ms); 31 } catch (InterruptedException ie) { 32 System.out.println("Snooze: " + ie.getMessage()); 33 } 34 } 35 36 public static WeakReference<FinalizerTest> makeRef() { 37 /* 38 * Make ft in another thread, so there is no danger of 39 * a conservative reference leaking onto the main thread's 40 * stack. 41 */ 42 43 final List<WeakReference<FinalizerTest>> wimp = 44 new ArrayList<WeakReference<FinalizerTest>>(); 45 Thread t = new Thread() { 46 public void run() { 47 FinalizerTest ft = new FinalizerTest("wahoo"); 48 wimp.add(new WeakReference<FinalizerTest>(ft)); 49 ft = null; 50 } 51 }; 52 53 t.start(); 54 55 try { 56 t.join(); 57 } catch (InterruptedException ie) { 58 throw new RuntimeException(ie); 59 } 60 61 return wimp.get(0); 62 } 63 64 public static String wimpString(final WeakReference<FinalizerTest> wimp) { 65 /* 66 * Do the work in another thread, so there is no danger of a 67 * conservative reference to ft leaking onto the main thread's 68 * stack. 69 */ 70 71 final String[] s = new String[1]; 72 Thread t = new Thread() { 73 public void run() { 74 FinalizerTest ref = wimp.get(); 75 if (ref != null) { 76 s[0] = ref.toString(); 77 } 78 } 79 }; 80 81 t.start(); 82 83 try { 84 t.join(); 85 } catch (InterruptedException ie) { 86 throw new RuntimeException(ie); 87 } 88 89 return s[0]; 90 } 91 92 public static void main(String[] args) { 93 WeakReference<FinalizerTest> wimp = makeRef(); 94 95 System.out.println("wimp: " + wimpString(wimp)); 96 97 /* this will try to collect and finalize ft */ 98 System.out.println("gc"); 99 Runtime.getRuntime().gc(); 100 101 System.out.println("wimp: " + wimpString(wimp)); 102 System.out.println("finalize"); 103 System.runFinalization(); 104 System.out.println("wimp: " + wimpString(wimp)); 105 106 System.out.println("sleep"); 107 snooze(1000); 108 109 System.out.println("reborn: " + FinalizerTest.mReborn); 110 System.out.println("wimp: " + wimpString(wimp)); 111 System.out.println("reset reborn"); 112 Runtime.getRuntime().gc(); 113 FinalizerTest.mReborn = FinalizerTest.mNothing; 114 System.out.println("gc + finalize"); 115 System.gc(); 116 System.runFinalization(); 117 118 System.out.println("sleep"); 119 snooze(1000); 120 121 System.out.println("reborn: " + FinalizerTest.mReborn); 122 System.out.println("wimp: " + wimpString(wimp)); 123 } 124 125 public static class FinalizerTest { 126 public static FinalizerTest mNothing = new FinalizerTest("nothing"); 127 public static FinalizerTest mReborn = mNothing; 128 129 private final String message; 130 private boolean finalized = false; 131 132 public FinalizerTest(String message) { 133 this.message = message; 134 } 135 136 public String toString() { 137 return "[FinalizerTest message=" + message + 138 ", finalized=" + finalized + "]"; 139 } 140 141 protected void finalize() { 142 finalized = true; 143 mReborn = this; 144 } 145 } 146 } 147
