lk146-LRU-LinkedHashMap.java

class LRUCache {
    int cap;
    LinkedHashMap<Integer,Integer> cache = new LinkedHashMap<>();
    public LRUCache(int capacity) {
        this.cap = capacity;
    }

    public int get(int key) {
        if(!cache.containsKey(key)){
            return -1;
        }
        makeRecently(key);
        return cache.get(key);
    }

    public void put(int key, int value) {
        if(cache.containsKey(key)){
            cache.put(key,value);
            makeRecently(key);
            return;
        }
        if(cache.size()>= this.cap) {
            //链表头部就是最久未使用的key
            int oldestKey = cache.keySet().iterator().next();
            cache.remove(oldestKey);
        }
        cache.put(key,value);
    }
    public void makeRecently(int key){
        int val = cache.get(key);
        cache.remove(key);
        cache.put(key,val);
    }
}

/**
 * Your LRUCache object will be instantiated and called as such:
 * LRUCache obj = new LRUCache(capacity);
 * int param_1 = obj.get(key);
 * obj.put(key,value);
 */