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1
8
9 package com.hp.hpl.jena.util.cache;
10
11 import java.util.Collection  ;
12 import java.util.HashMap ;
13 import java.util.Iterator ;
14
15 import org.apache.commons.logging.Log;
16 import org.apache.commons.logging.LogFactory;
17
18
22 public class RandCache implements Cache, CacheControl {
23 int size;
24 int threshhold;
25 boolean enabled = true;
26 String name;
29 HashMap map;
30 Collection collection;
31
32 protected static Log logger = LogFactory.getLog(RandCache.class);
33
34 long gets = 0;
35 long puts = 0;
36 long hits = 0;
37
38
39 RandCache(String name, int size) {
40 this.size = size;
41 try {
42 map = new HashMap (size * 100 / 75); } catch (IllegalArgumentException e) {
44 if ("Illegal load factor: NaN".equals(e.getMessage())) {
45 logger.warn("Detected a NaN anomaly believed to be due to use of JDK 1.4.1");
54 map = new HashMap (size*100/75, 0.75f);
55 } else {
56 throw e;
57 }
58 }
59 threshhold = size;
60 if (threshhold < 2) {
61 throw new Error ("Cache size too small: " + size);
62 }
63 collection = map.values();
64 }
65
66 public synchronized Object get(Object key) {
67 if (enabled) {
68 if (gets == Long.MAX_VALUE) {
69 forgetStats();
70 }
71 gets++;
72 Object result = map.get(key);
73 if (result != null) {
74 hits++;
75 }
76 return result;
77 } else {
78 return null;
79 }
80 }
81
82 public synchronized void put(Object key, Object value) {
83
84 if (value == null) {
86 throw new NullPointerException ();
87 }
88
89 if (enabled) {
90 if (puts == Long.MAX_VALUE) {
91 forgetStats();
92 }
93 puts++;
94 if (map.size() >= threshhold) {
95 makeSpace();
96 }
97 map.put(key, value);
98 }
99 }
100
101 protected void makeSpace() {
102 Iterator iter = collection.iterator();
103
104 int size = map.size();
106 int i = 3;
107 while (i < size ) {
108 iter.next();
109 iter.remove();
110 iter.next();
111 iter.next();
112 i = i + 3;
113 }
114 }
115
116 public synchronized boolean getEnabled() {
117 return enabled;
118 }
119
120 public synchronized boolean setEnabled(boolean enabled) {
121 boolean result = enabled;
122 this.enabled = enabled;
123 return result;
124 }
125
126 public synchronized void clear() {
127 map.clear();
128 }
129
130 public synchronized long getHits() {
131 return hits;
132 }
133
134 public synchronized long getGets() {
135 return gets;
136 }
137
138 public synchronized long getPuts() {
139 return puts;
140 }
141
142 protected void forgetStats() {
143 gets = gets/2;
144 puts = puts/2;
145 hits = hits/2;
146 }
147
148 }
149
179 |
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