1 // Test of WeakReference

     2 

     3 // Copyright (C) 2001 Red Hat, Inc.

     4 

     5 // This file is part of Mauve.

     6 

     7 // Mauve is free software; you can redistribute it and/or modify

     8 // it under the terms of the GNU General Public License as published by

     9 // the Free Software Foundation; either version 2, or (at your option)

    10 // any later version.

    11 

    12 // Mauve is distributed in the hope that it will be useful,

    13 // but WITHOUT ANY WARRANTY; without even the implied warranty of

    14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    15 // GNU General Public License for more details.

    16 

    17 // You should have received a copy of the GNU General Public License

    18 // along with Mauve; see the file COPYING.  If not, write to

    19 // the Free Software Foundation, 59 Temple Place - Suite 330,

    20 // Boston, MA 02111-1307, USA.

    21 

    22 // Tags: JDK1.2

    23 

    24 // In this test we make some assumptions about how the GC operates

    25 // that are probably not quite sound.  In particular we assume

    26 // System.gc() will collect everything.

    27 

    28 package gnu.testlet.java.lang.ref.WeakReference;

    29 

    30 import gnu.testlet.Testlet;

    31 import gnu.testlet.TestHarness;

    32 import java.lang.ref.*;

    33 

    34 public class weakref implements Testlet

    35 {

    36 

    37   static class Reffer extends Thread

    38   {

    39     ReferenceQueue q;

    40     TestHarness harness;

    41     WeakReference wr;

    42     Integer twt;

    43 

    44     public Reffer (ReferenceQueue q, TestHarness harness)

    45     {

    46       this.q = q;

    47       this.harness = harness;

    48     }

    49 

    50     public void run()

    51     {

    52       twt = new Integer (23);

    53       wr = new WeakReference (twt, q);

    54 

    55       System.gc ();

    56 

    57       Reference r = q.poll ();

    58       harness.check (r, null, "live reference");

    59       harness.check (wr.get (), twt);

    60     }

    61   }

    62 

    63   public void test (TestHarness harness)

    64   {

    65     ReferenceQueue q = new ReferenceQueue ();

    66 

    67     // Create reference in a separate thread so no inadvertent references

    68     // to the contained object are left on the stack, which causes VM's that

    69     // do conservative stack GC scans to report false negatives for this test.

    70     Reffer reffer = new Reffer(q, harness); 

    71     reffer.start();

    72     try {

    73       reffer.join();

    74     } catch (InterruptedException e) {

    75       throw new RuntimeException(e);

    76     }

    77     WeakReference wr = reffer.wr;

    78 

    79     // Weak reference "should" get cleared here

    80     reffer.twt = null;

    81     System.gc ();

    82 

    83     Reference r = null;

    84     try

    85       {

    86 	r = q.remove (5 * 1000); // 5 seconds.

    87       }

    88     catch (InterruptedException _)

    89       {

    90 	harness.debug (_);

    91       }

    92 

    93     harness.check (r, wr, "unreachable");

    94     harness.check (wr.get (), null, "contents of weak reference");

    95   }

    96 }