caching - How would you implement an LRU cache in Java? -

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please don't ehcache or oscache, etc. assume purposes of question want implement own using sdk (learning doing). given cache used in multithreaded environment, datastructures use? i've implemented 1 using linkedhashmap , collections#synchronizedmap, i'm curious if of new concurrent collections better candidates.

update: reading through yegge's latest when found nugget:

if need constant-time access , want maintain insertion order, can't better linkedhashmap, wonderful data structure. way possibly more wonderful if there concurrent version. alas.

i thinking same thing before went linkedhashmap + collections#synchronizedmap implementation mentioned above. nice know hadn't overlooked something.

based on answers far, sounds best bet highly concurrent lru extend concurrenthashmap using of same logic linkedhashmap uses.

i lots of these suggestions, think i'll stick linkedhashmap + collections.synchronizedmap. if revisit in future, i'll work on extending concurrenthashmap in same way linkedhashmap extends hashmap.

update:

by request, here's gist of current implementation.

private class lrucache<a, b> extends linkedhashmap<a, b> {     private final int maxentries;      public lrucache(final int maxentries) {         super(maxentries + 1, 1.0f, true);         this.maxentries = maxentries;     }      /**      * returns <tt>true</tt> if <code>lrucache</code> has more entries maximum specified when      * created.      *      * <p>      * method <em>does not</em> modify underlying <code>map</code>; relies on implementation of      * <code>linkedhashmap</code> that, behavior documented in javadoc      * <code>linkedhashmap</code>.      * </p>      *      * @param eldest      *            <code>entry</code> in question; implementation doesn't care is, since      *            implementation dependent on size of cache      * @return <tt>true</tt> if oldest      * @see java.util.linkedhashmap#removeeldestentry(map.entry)      */     @override     protected boolean removeeldestentry(final map.entry<a, b> eldest) {         return super.size() > maxentries;     } }  map<string, string> example = collections.synchronizedmap(new lrucache<string, string>(cache_size));

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