手动实现Redis的LRU缓存机制示例详解

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亲爱的编程学习爱好者，如果你点开了这篇文章，说明你对《手动实现Redis的LRU缓存机制示例详解》很感兴趣。本篇文章就来给大家详细解析一下，主要介绍一下缓存、RedisLRU，希望所有认真读完的童鞋们，都有实质性的提高。

第一种实现(使用LinkedHashMap)

public class LRUCache {

  int capacity;
  Map
   
     map;

  public LRUCache(int capacity){
    this.capacity = capacity;
    map = new LinkedHashMap();
  }

  public int get(int key){
    //如果没有找到
    if (!map.containsKey(key)){
      return -1;
    }
    //找到了就刷新数据
    Integer value = map.remove(key);
    map.put(key,value);
    return value;
  }

  public void put(int key,int value){
    if (map.containsKey(key)){
      map.remove(key);
      map.put(key,value);
      return;
    }
    map.put(key,value);
    //超出capacity，删除最久没用的即第一个,或者可以复写removeEldestEntry方法
    if (map.size() > capacity){
      map.remove(map.entrySet().iterator().next().getKey());
    }
  }

  public static void main(String[] args) {
    LRUCache lruCache = new LRUCache(10);
    for (int i = 0; i 


    


    
第二种实现(双链表+hashmap)


    
public class LRUCache {

  private int capacity;
  private Map
     
      map;
  private ListNode head;
  private ListNode tail;

  public LRUCache2(int capacity){
    this.capacity = capacity;
    map = new HashMap();
    head = new ListNode(-1,-1);
    tail = new ListNode(-1,-1);
    head.next = tail;
    tail.pre = head;
  }

  public int get(int key){
    if (!map.containsKey(key)){
      return -1;
    }
    ListNode node = map.get(key);
    node.pre.next = node.next;
    node.next.pre = node.pre;
    return node.val;
  }

  public void put(int key,int value){
    if (get(key)!=-1){
      map.get(key).val = value;
      return;
    }
    ListNode node = new ListNode(key,value);
    map.put(key,node);
    moveToTail(node);

    if (map.size() > capacity){
      map.remove(head.next.key);
      head.next = head.next.next;
      head.next.pre = head;
    }
  }

  //把节点移动到尾巴
  private void moveToTail(ListNode node) {
    node.pre = tail.pre;
    tail.pre = node;
    node.pre.next = node;
    node.next = tail;
  }

  //定义双向链表节点
  private class ListNode{
    int key;
    int val;
    ListNode pre;
    ListNode next;

    //初始化双向链表
    public ListNode(int key,int val){
      this.key = key;
      this.val = val;
      pre = null;
      next = null;
    }
  }
}
     
像第一种方式，如果复写removeEldestEntry会更简单，这里简单的展示一下
public class LRUCache extends LinkedHashMap
     
       {
  private int capacity;
  
  @Override
  protected boolean removeEldestEntry(Map.Entry
      
        eldest) { return size() > capacity; } }