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<TITLE>Implementing a Least-Recently-Used (LRU) Cache
(Java Developers Almanac Example)
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<h3>
e344.
Implementing a Least-Recently-Used (LRU) Cache</h3>
<pre>
// Create cache
final int MAX_ENTRIES = <font color="#0066ff"><i>100</i></font>;
Map cache = new LinkedHashMap(MAX_ENTRIES+1, .75F, true) {
// This method is called just after a new entry has been added
public boolean removeEldestEntry(Map.Entry eldest) {
return size() > MAX_ENTRIES;
}
};
// Add to cache
Object key = <font color="#0066ff"><i>"key"</i></font>;
cache.put(key, <font color="#0066ff"><i>object</i></font>);
// Get object
Object o = cache.get(key);
if (o == null && !cache.containsKey(key)) {
// Object not in cache. If null is not a possible value in the cache,
// the call to cache.contains(key) is not needed
}
// If the cache is to be used by multiple threads,
// the cache must be wrapped with code to synchronize the methods
cache = (Map)Collections.synchronizedMap(cache);
</pre>
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Related Examples
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e342. <a class="eglink" href="coll_Queue.html?l=rel">
Implementing a Queue
</a>
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e343. <a class="eglink" href="coll_Stack.html?l=rel">
Implementing a Stack
</a>
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e345. <a class="eglink" href="coll_Iterate.html?l=rel">
Listing the Elements of a Collection
</a>
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e346. <a class="eglink" href="coll_StorePrimitive.html?l=rel">
Storing Primitive Types in a Collection
</a>
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e347. <a class="eglink" href="coll_CreateCopy.html?l=rel">
Creating a Copy of a Collection
</a>
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e348. <a class="eglink" href="coll_MakeRo.html?l=rel">
Making a Collection Read-Only
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See also:
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Arrays">
Arrays
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Bits">
Bits
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Dates">
Dates
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Hash%20Tables">
Hash Tables
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Lists">
Lists
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Property%20Files">
Property Files
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sets">
Sets
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sorted%20Collections">
Sorted Collections
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Time">
Time
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Timers">
Timers
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