【LeetCode】LRU Cache

设计和实现一个  LRU (最近最少使用) 缓存机制。它应该支持以下操作： 获取数据 get 和 写入数据 put 

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package letcode;   import java.util.HashMap; import java.util.Map;   /**  * 双向链表+HashMap  *  * @author zeze  *  */ public class LRUCache {                 public static void main(String[] args) {           /*char key = 0;         int value = 0;         LRUCache obj = new LRUCache(capacity);         int param_1 = obj.get(key);         obj.put(key, value);*/       }       int capacity;     Map<Integer, Node> map = new HashMap<Integer, Node>();     Node head = null;     Node end = null;           public LRUCache(int capacity) {         this.capacity = capacity;     }       public int get(int key) {           if (map.containsKey(key)) {             Node temp = map.get(key);             remove(temp);// 移除节点             setHead(temp);// 将节点设置为头结点             return temp.value;         }         return -1;     }           public void put(int key, int value) {         if (map.containsKey(key)) {// 更新节点             Node old = map.get(key);             old.value = value;             remove(old);             setHead(old);         } else {// 插入节点             Node created = new Node(key, value);             if (map.size() >= capacity) {                 map.remove(end.key);// HashMap中移除尾节点                 remove(end);// 链表中移除尾节点                 setHead(created);             } else {                 setHead(created);             }             map.put(key, created);         }     }       private void setHead(Node n) {         n.next = head;         n.pre = null;         if (head != null) {             head.pre = n;         }         head = n;         if (end == null)             end = head;       }       private void remove(Node n) {         if (n.pre != null)             n.pre.next = n.next;         else             head = n.next;         if (n.next != null)             n.next.pre = n.pre;         else             end = n.pre;       }         }   class Node {     int key;     int value;     Node pre;     Node next;       Node(int key, int value) {         this.key = key;         this.value = value;     } }