Implemention of LRU Cache

Source:

 import java.util.concurrent.ConcurrentHashMap;  
 import java.util.concurrent.ConcurrentLinkedDeque;  

 /**  
  * Class LRU Cache  
  * @author Shashwat  
  * @param <Key>  
  * @param <Value>  
  */  
 public class LRUCache<Key, Value> {  
      private final int MAX_SIZE;  
      private ConcurrentHashMap<Key, Value> map;  
      private ConcurrentLinkedDeque<Key> queue;  
      public LRUCache(final int maxSize) {  
           this.MAX_SIZE = maxSize;  
           this.map = new ConcurrentHashMap<Key, Value>(this.MAX_SIZE);  
           this.queue = new ConcurrentLinkedDeque<Key>();            
      }  
      public Value get(Key key) {  
           return this.map.get(key);  
      }  
      public void put(final Key key, final Value value) {  
           if (this.map.containsKey(key)) {  
                this.queue.remove(key);  
           }  
           while (this.queue.size() >= this.MAX_SIZE) {  
                Key oldKey = this.queue.poll();  
                if (null != oldKey) {  
                     this.map.remove(oldKey);  
                }  
           }  
           this.queue.add(key);  
           this.map.put(key, value);  
      }  
 }