tests/weakref.java

   1 import java.lang.ref.*;
   2 import java.util.HashSet;
   3
   4 class weakref {
   5         class OtherThread extends Thread {
   6                 public volatile boolean quitNow = false;
   7                 private final ReferenceQueue q;
   8                 private final HashSet h;
   9                 public OtherThread(ReferenceQueue q, HashSet h) {
  10                         this.q = q;
  11                         this.h = h;
  12                 }
  13                 public void run() {
  14                         while (!quitNow) {
  15                                 try {
  16                                         MyRef r = (MyRef) q.remove();
  17                                         h.remove(r);
  18                                         System.out.println("Integer: " + Integer.toString(r.val));
  19                                 } catch (InterruptedException e) {
  20                                 }
  21                         }
  22                 }
  23         }
  24
  25         class MyRef extends WeakReference {
  26                 public final int val;
  27                 MyRef(Object o, ReferenceQueue q, int val) {
  28                         super(o, q);
  29                         this.val = val;
  30                 }
  31         }
  32
  33         private void test() {
  34                 System.out.println("This should print a long list of Integers if weak references are working.");
  35                 ReferenceQueue q = new ReferenceQueue();
  36                 HashSet h = new HashSet();
  37                 OtherThread t = new OtherThread(q, h);
  38                 t.start();
  39                 for (int i=0; i<1000000; i++) {
  40                         Object o = new Integer(i);
  41                         Reference r = new MyRef(o, q, i);
  42                         h.add(r);
  43                 }
  44                 Runtime.getRuntime().gc();
  45                 try {
  46                         Thread.sleep(1000);
  47                         t.quitNow = true;
  48                         t.interrupt();
  49                         t.join();
  50                 } catch (InterruptedException e) {
  51                 }
  52         }
  53
  54         public static void main(String[] args) {
  55                 new weakref().test();
  56         }
  57 }
  58
  59 /*
  60  * These are local overrides for various environment variables in Emacs.
  61  * Please do not remove this and leave it at the end of the file, where
  62  * Emacs will automagically detect them.
  63  * ---------------------------------------------------------------------
  64  * Local variables:
  65  * mode: java
  66  * indent-tabs-mode: t
  67  * c-basic-offset: 4
  68  * tab-width: 4
  69  * End:
  70  * vim:noexpandtab:sw=4:ts=4:
  71  */