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1
19 package org.objectweb.carol.cmi;
20
21 import java.lang.ref.WeakReference  ;
22 import java.lang.ref.ReferenceQueue ;
23
24
28 public class WeakCache {
29 private java.util.HashMap table = new java.util.HashMap ();
30
31 private class WeakRef extends WeakReference {
32 private int hash;
33
34 public WeakRef(Object obj) {
35 super(obj);
36 hash = obj.hashCode();
37 }
38
39 public WeakRef(Object obj, ReferenceQueue rq) {
40 super(obj, rq);
41 hash = obj.hashCode();
42 }
43
44 public int hashCode() {
45 return hash;
46 }
47
48 public boolean equals(Object obj) {
49 if (obj == this) {
51 return true;
52 }
53
54 if (obj instanceof WeakRef) {
55 Object o = this.get();
56 return (o != null) && o.equals(((WeakRef) obj).get());
57 } else
58 return false;
59 }
60
61 public void remove() {
62 synchronized (table) {
63 table.remove(this);
64 }
65 }
66 }
67
68 private static ReferenceQueue rQueue = new ReferenceQueue ();
69 private static Thread rQueueThread = new RefQueueFlush();
70 static {
71 rQueueThread.setDaemon(true);
72 rQueueThread.start();
73 }
74
75 private static class RefQueueFlush extends Thread {
76 public RefQueueFlush() {
77 }
78 public void run() {
79 while (true) {
80 try {
81 WeakRef wr = (WeakRef) rQueue.remove();
82 wr.remove();
83 } catch (InterruptedException e) {
84 }
86 }
87 }
88 }
89
90
95 public Object getCached(Object obj) {
96 WeakRef wr = new WeakRef(obj, rQueue);
97 synchronized (table) {
98 WeakRef cached = (WeakRef) table.get(wr);
99 if (cached == null) {
100 table.put(wr, wr);
101 return obj;
102 }
103 Object c = cached.get();
104 if (c == null) {
105 table.remove(cached);
106 table.put(wr, wr);
107 return obj;
108 }
109 return c;
110 }
111 }
112 }
113 |
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