leetcode146 LRU缓存机制(java)

LRU缓存机制
题意：构造一个有LRU缓存机制的容器即写一个类并实现get和put
通过jdk中的LinkedHashMap中的构造函数我们可以发现，jdk已经实现了LRU这一机制了

LinedHashMap的构造函数如下：

public LinkedHashMap(int initialCapacity,
                         float loadFactor,
                         boolean accessOrder) {
     
        super(initialCapacity, loadFactor);
        this.accessOrder = accessOrder;
    }

我们可以根据设置accessOrder变量来实现容器的LRU机制，对get和put的实现也是基于这一机制
代码如下：

package com.ischen.demo.utils.leetcode;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;

/**
 * @Author：ischen
 * @Date 2019/7/29 10:18
 * @Describe
 */
public class LRUCache {
     
    HashMap<Integer,Integer> map;
    int size;
    public LRUCache(int capacity) {
     
        size = capacity;
        map = new LinkedHashMap<Integer, Integer>(capacity,0.75f,true);
    }

    public int get(int key) {
     
        return map.containsKey(key)?map.get(key):-1;
    }

    public void put(int key, int value) {
     
        if(map.containsKey(key)){
     
            map.put(key,value);
            return;
        }
        if(map.size()>=size){
     
            Iterator<Integer> i = map.keySet().iterator();
            if(i.hasNext()){
     
                map.remove(i.next());
            }
        }
        map.put(key,value);
    }

    public static void main(String[] args) {
     
        LRUCache cache = new LRUCache(2);
        System.out.println(cache.get(2));
        cache.put(2,6);
        System.out.println(cache.get(1));
        cache.put(1,5);
        cache.put(1,2);
        System.out.println(cache.get(1));
        System.out.println(cache.get(2));
    }
}