HARD/src/hard/LRUCache_use_LinkedHashMap.java

fishercoder1534 · fishercoder1534 · commit d76dbfeb3ff4 · 2016-09-06T11:49:24.000-07:00
diff --git a/HARD/src/hard/LRUCache_use_LinkedHashMap.java b/HARD/src/hard/LRUCache_use_LinkedHashMap.java
@@ -0,0 +1,32 @@
+package hard;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**The shortest implementation is to use LinkedHashMap:
+ * specify a size of the linkedHashMap;
+ * override the removeEldestEntry method when its size exceeds max size: https://docs.oracle.com/javase/8/docs/api/java/util/LinkedHashMap.html#removeEldestEntry-java.util.Map.Entry-
+ * in the constructor, set the last boolean variable to be true: it means the ordering mode, if we set it to true, it means
+ * in access order, false, means it's in insertion order: https://docs.oracle.com/javase/8/docs/api/java/util/LinkedHashMap.html#LinkedHashMap-int-float-boolean-*/
+public class LRUCache_use_LinkedHashMap {
+    
+    private Map<Integer, Integer> cache;
+    private final int max;
+    
+    public LRUCache_use_LinkedHashMap(int capacity) {
+        max = capacity;
+        cache = new LinkedHashMap<Integer, Integer>(capacity, 1.0f, true){
+            public boolean removeEldestEntry(Map.Entry eldest){
+                return cache.size() > max;
+            }
+        };
+    }
+    
+    public int get(int key) {
+        return cache.getOrDefault(key, -1);
+    }
+    
+    public void set(int key, int value) {
+        cache.put(key, value);
+    }
+}
