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1
52
53 package com.go.trove.util;
54
55 import java.util.*;
56
57
69 public class Cache extends SoftHashMap {
70 private final int mMaxRecent;
71 private final UsageMap mUsageMap;
73
74
83 public Cache(int maxRecent) {
84 if (maxRecent <= 0) {
85 throw new IllegalArgumentException 
86 ("Max recent must be greater than zero: " + maxRecent);
87 }
88 mMaxRecent = maxRecent;
89 mUsageMap = new UsageMap();
90 }
91
92
99 public Cache(Cache cache) {
100 mMaxRecent = cache.mMaxRecent;
101 mUsageMap = cache.mUsageMap;
102 }
103
104 public Object get(Object key) {
105 Object value = super.get(key);
106 if (value != null || super.containsKey(key)) {
107 adjustMRU(key, value);
108 }
109 return value;
110 }
111
112 public Object put(Object key, Object value) {
113 if (value == null) {
114 value = new Null();
115 }
116 adjustMRU(key, value);
117 return super.put(key, value);
118 }
119
120 public Object remove(Object key) {
121 synchronized (mUsageMap) {
122 mUsageMap.remove(key);
123 }
124 return super.remove(key);
125 }
126
127 public void clear() {
128 super.clear();
129 synchronized (mUsageMap) {
130 mUsageMap.clear();
131 }
132 }
133
134 private void adjustMRU(Object key, Object value) {
135 synchronized (mUsageMap) {
136 Object existing = mUsageMap.get(key);
137
138 if (existing != null) {
139 if (value == null && existing instanceof Null) {
140 value = existing;
141 }
142 }
143 else {
144 if (!mUsageMap.containsKey(key)) {
145 while (mUsageMap.size() >= mMaxRecent) {
148 mUsageMap.remove(mUsageMap.lastKey());
149 }
150 }
151 }
152
153 mUsageMap.put(key, value);
154 }
155 }
156 }
157 |
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