tests/gc/LockRecords.java

   1 import java.util.Vector;
   2
   3 public class LockRecords {
   4         static final int N = 3;
   5
   6         static Vector v;
   7
   8         static class MyObject
   9         {
  10                 public int id;
  11                 public int counter;
  12
  13                 protected void finalize() throws Throwable
  14                 {
  15                         System.out.println("\tObject #" + id + " gets finalized");
  16                         throw new Exception("Object #" + id + " is nasty!");
  17                 }
  18         };
  19
  20         static class MyThread extends Thread
  21         {
  22                 public String name;
  23                 public synchronized void run()
  24                 {
  25                         System.out.println("\t" + name + ": Starting ...");
  26                         try {
  27                                 for (int i=0; i<N; i++) {
  28                                         MyObject o = (MyObject) v.get(i);
  29                                         System.out.println("\t" + name + ": Trying on #" + o.id);
  30                                         synchronized(o) {
  31                                                 System.out.println("\t" + name + ": Locked on #" + o.id);
  32                                                 this.wait(200);
  33                                                 System.out.println("\t" + name + ": Releasing #" + o.id);
  34                                                 o.counter--;
  35                                         }
  36                                         while (o.counter > 0) {
  37                                                 this.wait(10);
  38                                         }
  39                                 }
  40                         } catch (Exception e) {
  41                                 e.printStackTrace();
  42                         }
  43                         System.out.println("\t" + name + ": finished.");
  44                 }
  45         };
  46
  47         public synchronized void test()
  48         {
  49                 System.out.println("Creating Objects ...");
  50                 v = new Vector();
  51                 for (int i=0; i<N; i++) {
  52                         MyObject o = new MyObject();
  53                         o.id = i;
  54                         o.counter = 2;
  55                         v.add(o);
  56                 }
  57
  58                 System.out.println("Starting Blocking Threads A + B...");
  59                 MyThread threadA = new MyThread();
  60                 MyThread threadB = new MyThread();
  61                 threadA.name = "A"; threadA.start();
  62                 threadB.name = "B"; threadB.start();
  63                 try {
  64                         threadA.join();
  65                         threadB.join();
  66                 } catch (Exception e) {
  67                         e.printStackTrace();
  68                 }
  69
  70                 System.out.println("Cleaning up ...");
  71                 v = null;
  72                 System.gc();
  73
  74                 System.out.println("Waiting some seconds ...");
  75                 try {
  76                         wait(3000);
  77                 } catch (Exception e) {
  78                         e.printStackTrace();
  79                 }
  80
  81                 System.out.println("Cleaning up again ...");
  82                 System.gc();
  83         }
  84
  85         public static void main(String args[])
  86         {
  87                 LockRecords test = new LockRecords();
  88                 test.test();
  89         }
  90 }