get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
set(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it should invalidate the least recently used item before inserting a new item.

 1 package Algorithms.hash; 2  3 import java.util.LinkedHashMap; 4 import java.util.Map; 5  6 public class LRUCache2 { 7     public static void main(String[] strs) { 8         LRUCache2 lrc2 = new LRUCache2(2); 9         lrc2.set(1,3);10         lrc2.set(2,2);11         lrc2.set(1,4);12         lrc2.set(4,2);13         14         System.out.println(lrc2.get(1));15     }16     17     LinkedHashMap<Integer, Integer> map;18     int capacity;19     20     public LRUCache2(final int capacity) {21         // create a map.22         map = new LinkedHashMap<Integer, Integer>(capacity) {23             /**24              * 25              */26             private static final long serialVersionUID = 1L;27 28             protected boolean removeEldestEntry(Map.Entry eldest) {29                 return size() > capacity;30             }31         };32         this.capacity = capacity;33     }34     35     public int get(int key) {36         Integer ret = map.get(key);37         if (ret == null) {38             return -1;39         } else {40             map.remove(key);41             map.put(key, ret);42         }43         44         return ret;45     }46     47     public void set(int key, int value) {48         map.remove(key);49         map.put(key, value);50     }51 }