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1 package org.shiftone.cache.util;
2
3
4
5 import java.lang.ref.Reference  ;
6 import java.lang.ref.ReferenceQueue ;
7 import java.lang.ref.WeakReference ;
8 import java.util.*;
9
10
11
15 public class WeakMap implements Map
16 {
17
18 private static final Log LOG = new Log(WeakMap.class);
19 private ReferenceQueue referenceQueue = new ReferenceQueue ();
20 private Map referenceMap = new TreeMap();
21
22 public Object put(Object key, Object value)
23 {
24
25 purge();
26
27 return referenceMap.put(key, new KeyedWeakReference(key, value));
28 }
29
30
31 public void putAll(Map map)
32 {
33
34 Set set = map.entrySet();
35 Iterator iterator = set.iterator();
36
37 while (iterator.hasNext())
38 {
39 Map.Entry entry = (Map.Entry) iterator.next();
40
41 put(entry.getKey(), entry.getValue());
42 }
43 }
44
45
46 public Object get(Object key)
47 {
48
49 purge();
50
51 Reference ref = (Reference ) referenceMap.get(key);
52
53 return (ref != null)
54 ? ref.get()
55 : null;
56 }
57
58
59 public void clear()
60 {
61 purge();
62 referenceMap.clear();
63 }
64
65
66 public Object remove(Object key)
67 {
68
69 purge();
70
71 return referenceMap.remove(key);
72 }
73
74
75 public Set keySet()
76 {
77
78 purge();
79
80 return referenceMap.keySet();
81 }
82
83
84 public boolean containsKey(Object key)
85 {
86
87 purge();
88
89 return referenceMap.containsKey(key);
90 }
91
92
93 public int size()
94 {
95
96 purge();
97
98 return referenceMap.size();
99 }
100
101
102 public boolean isEmpty()
103 {
104
105 purge();
106
107 return referenceMap.isEmpty();
108 }
109
110
111 public void purge()
112 {
113
114 KeyedWeakReference ref;
115
116 while ((ref = (KeyedWeakReference) referenceQueue.poll()) != null)
117 {
118 LOG.info("referenceQueue purge : " + ref.getKey() + " ; size=" + size());
119 referenceMap.remove(ref.getKey());
120 }
121 }
122
123
124 public boolean containsValue(Object value)
125 {
126 throw new UnsupportedOperationException ("containsValue");
127 }
128
129
130 public Collection values()
131 {
132 throw new UnsupportedOperationException ("values");
133 }
134
135
136 public Set entrySet()
137 {
138 throw new UnsupportedOperationException ("entrySet");
139 }
140
141
142 class KeyedWeakReference extends WeakReference
143 {
144
145 private final Object key;
146
147 public KeyedWeakReference(Object key, Object referent)
148 {
149
150 super(referent, referenceQueue);
151
152 this.key = key;
153 }
154
155
156 public Object getKey()
157 {
158 return key;
159 }
160 }
161 }
162 |
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