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comparison src/main/java/edu/harvard/iq/dataverse/util/LruCache.java @ 10:a50cf11e5178

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Rewrite LGDataverse completely upgrading to dataverse4.0
author Zoe Hong <zhong@mpiwg-berlin.mpg.de>
date Tue, 08 Sep 2015 17:00:21 +0200
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9:5926d6419569 10:a50cf11e5178
1 package edu.harvard.iq.dataverse.util;
2
3 import java.util.LinkedHashMap;
4 import java.util.concurrent.locks.ReentrantLock;
5
6 /**
7 * A thread-safe implementation of a capped-size cache, where the removal is done
8 * based on the "Least Recently Used" strategy.
9 * This implementation allows some scenarios where the removed values are not the
10 * least recently used, in order to provide better performance.
11 *
12 * @author michael
13 * @param <K> Class for the cache keys
14 * @param <V> Class for the cache values
15 */
16 public class LruCache<K,V> {
17 private final LinkedHashMap<K, V> cache = new LinkedHashMap<>(10, 0.75f, true);
18 private final ReentrantLock cacheLock = new ReentrantLock();
19 private long maxSize = 128;
20
21 /**
22 * @param k The key to get
23 * @return The value associated with {@code k}, or {@code null}, if there isn't any.
24 */
25 public V get( K k ) {
26 try {
27 cacheLock.lock();
28 return cache.get(k);
29 } finally { cacheLock.unlock(); }
30 }
31
32 /**
33 * Associates {@code k} with {@code v}.
34 * @param k the key
35 * @param v the value
36 * @return {@code v}, to allow method call chaining.
37 */
38 public V put( K k, V v ) {
39 try {
40 cacheLock.lock();
41 cache.put(k, v);
42 shrinkToMaxSize();
43 return v;
44 } finally { cacheLock.unlock(); }
45 }
46
47 public long size() {
48 try {
49 cacheLock.lock();
50 return cache.size();
51 } finally { cacheLock.unlock(); }
52 }
53
54 public long getMaxSize() {
55 return maxSize;
56 }
57
58 public void setMaxSize(long maxSize) {
59 if ( maxSize < 1 ) {
60 throw new IllegalArgumentException("Max cache size can't be less than 1");
61 }
62 try {
63 cacheLock.lock();
64 this.maxSize = maxSize;
65 shrinkToMaxSize();
66 } finally { cacheLock.unlock(); }
67 }
68
69 public void invalidate() {
70 try {
71 cacheLock.lock();
72 cache.clear();
73 } finally { cacheLock.unlock(); }
74 }
75
76 public void invalidate( K k ) {
77 try {
78 cacheLock.lock();
79 cache.remove(k);
80 } finally { cacheLock.unlock(); }
81 }
82
83 private void shrinkToMaxSize() {
84 while( cache.size() > getMaxSize() ) {
85 cache.remove( cache.entrySet().iterator().next().getKey() );
86 }
87 }
88 }