146. LRU 缓存 (opens new window)

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;
        }
        makeRecent(key);
        return cache.get(key);
    }
    
    public void put(int key, int value) {
        if(cache.containsKey(key)){
            cache.put(key,value);
            makeRecent(key);
            return ;
        }
        if(cache.size()>=this.cap){
            int oldKey = cache.keySet().iterator().next();
            cache.remove(oldKey);
        }
        //没有该key且<size
        cache.put(key,value);
    }

    void makeRecent(int key){
        int val = cache.get(key);
        cache.remove(key);
        cache.put(key,val);
    }
}