1 /*
   2  * Copyright (c) 1997, 1998, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /* @test
  25  * @summary Basic functional test of reference objects
  26  * @author Mark Reinhold
  27  */
  28 
  29 
  30 import java.lang.ref.*;
  31 import java.util.Vector;
  32 
  33 
  34 public class Basic {
  35 
  36     static ReferenceQueue q = new ReferenceQueue();
  37     static ReferenceQueue q2 = new ReferenceQueue();
  38     static Reference rw, rw2, rp, rp2;
  39     static Vector keep = new Vector();
  40     static boolean finalized = false;
  41 
  42     public static class ClearFinalizerThread {
  43         protected void finalize() {
  44             System.err.println("Cleared finalizer thread");
  45         }
  46     };
  47 
  48     protected void finalize() {
  49         Basic.finalized = true;
  50         System.err.println("Finalized " + this);
  51     }
  52 
  53     public static class Sub { };
  54 
  55     Object sub = new Sub();
  56 
  57     static void fork(Runnable proc) throws InterruptedException {
  58         Thread t = new Thread(proc);
  59         t.start();
  60         t.join();
  61     }
  62 
  63     static void showReferences() throws InterruptedException {
  64         fork(new Runnable() {
  65             public void run() {
  66                 System.err.println("References: W " + rw.get()
  67                                    + ", W2 " + rw2.get()
  68                                    + ", P " + rp.get()
  69                                    + ", P2 " + rp2.get());
  70             }
  71         });
  72     }
  73 
  74     static void createNoise() throws InterruptedException {
  75         fork(new Runnable() {
  76             public void run() {
  77                 keep.addElement(new PhantomReference(new Object(), q2));
  78             }
  79         });
  80     }
  81 
  82 
  83     public static void main(String[] args) throws Exception {
  84 
  85         fork(new Runnable() {
  86             public void run() {
  87                 Basic s = new Basic();
  88                 rw = new WeakReference(s, q);
  89                 rw2 = new WeakReference(s);
  90                 rp = new PhantomReference(s, q);
  91                 rp2 = new PhantomReference(s.sub, q);
  92                 s = null;
  93             }
  94         });
  95 
  96         showReferences();
  97 
  98         int ndq = 0;
  99         boolean prevFinalized = false;
 100     outer:
 101         for (int i = 1;; i++) {
 102             Reference r;
 103 
 104             createNoise();
 105             System.err.println("GC " + i);
 106             Thread.sleep(10);
 107             System.gc();
 108 
 109             showReferences();
 110             while ((r = q2.poll()) != null) {
 111                 System.err.println("Noise " + r);
 112             }
 113 
 114             /* Cause a dummy object to be finalized, since the finalizer thread
 115                might retain a reference to the Basic instance after it's been
 116                finalized (this happens with java_g) */
 117             if (Basic.finalized && !prevFinalized) {
 118                 fork(new Runnable() {
 119                     public void run() {
 120                         new ClearFinalizerThread();
 121                     }});
 122                 prevFinalized = true;
 123             }
 124 
 125             while ((r = q.poll()) != null) {
 126                 ndq++;
 127                 if (r != null) {
 128                     System.err.println("Dequeued " + r);
 129                     if (ndq == 3) break outer;
 130                 }
 131             }
 132 
 133             if (i >= 10) break;
 134 
 135         }
 136 
 137         if (ndq != 3) {
 138             throw new Exception("Expected to dequeue 3 reference objects,"
 139                                 + " but only got " + ndq);
 140         }
 141 
 142         if (! Basic.finalized) {
 143             throw new Exception("Test object not finalized");
 144         }
 145 
 146     }
 147 
 148 }