Home | History | Annotate | Download | only in src 
      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 {
     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 
     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 
     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 
     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