1 // Copyright 2008 The Android Open Source Project 2 3 import java.lang.ref.WeakReference; 4 5 /** 6 * Some finalizer tests. 7 * 8 * This only works if System.runFinalization() causes finalizers to run 9 * immediately or very soon. 10 */ 11 public class Main { snooze(int ms)12 private static void snooze(int ms) { 13 try { 14 Thread.sleep(ms); 15 } catch (InterruptedException ie) { 16 System.out.println("Snooze: " + ie.getMessage()); 17 } 18 } 19 makeRef()20 public static WeakReference makeRef() { 21 /* 22 * Make ft in another thread, so there is no danger of 23 * a conservative reference leaking onto the main thread's 24 * stack. 25 */ 26 27 final WeakReference[] wimp = new WeakReference[1]; 28 Thread t = new Thread() { 29 public void run() { 30 FinalizerTest ft = new FinalizerTest("wahoo"); 31 wimp[0] = new WeakReference(ft); 32 ft = null; 33 } 34 }; 35 36 t.start(); 37 38 try { 39 t.join(); 40 } catch (InterruptedException ie) { 41 throw new RuntimeException(ie); 42 } 43 44 return wimp[0]; 45 } 46 wimpString(final WeakReference wimp)47 public static String wimpString(final WeakReference wimp) { 48 /* 49 * Do the work in another thread, so there is no danger of a 50 * conservative reference to ft leaking onto the main thread's 51 * stack. 52 */ 53 54 final String[] s = new String[1]; 55 Thread t = new Thread() { 56 public void run() { 57 Object ref = wimp.get(); 58 if (ref != null) { 59 s[0] = ref.toString(); 60 } 61 } 62 }; 63 64 t.start(); 65 66 try { 67 t.join(); 68 } catch (InterruptedException ie) { 69 throw new RuntimeException(ie); 70 } 71 72 return s[0]; 73 } 74 main(String[] args)75 public static void main(String[] args) { 76 WeakReference wimp = makeRef(); 77 78 System.out.println("wimp: " + wimpString(wimp)); 79 80 /* this will try to collect and finalize ft */ 81 System.out.println("gc"); 82 System.gc(); 83 84 System.out.println("wimp: " + wimpString(wimp)); 85 System.out.println("finalize"); 86 System.runFinalization(); 87 System.out.println("wimp: " + wimpString(wimp)); 88 89 System.out.println("sleep"); 90 snooze(1000); 91 92 System.out.println("reborn: " + FinalizerTest.mReborn); 93 System.out.println("wimp: " + wimpString(wimp)); 94 System.out.println("reset reborn"); 95 System.gc(); 96 FinalizerTest.mReborn = FinalizerTest.mNothing; 97 System.out.println("gc + finalize"); 98 System.gc(); 99 System.runFinalization(); 100 101 System.out.println("sleep"); 102 snooze(1000); 103 104 System.out.println("reborn: " + FinalizerTest.mReborn); 105 System.out.println("wimp: " + wimpString(wimp)); 106 } 107 } 108