import java.util.HashMap;
import java.util.Map;

public class Pair<K,V>{
    private K key;
    private V value;

    public Pair(K key,V value){
        this.key=key;
        this.value=value;
    }
    public K getKey(){
        return key;
    }
    public V getValue(){
        return value;
    }

    public Pair<V,K> swap(){
        return new Pair<>(this.value,this.key);
    }


    public class Cache<K,V>{
        private Map<K,V> storage;
        public Cache(){
            this.storage=new HashMap<>();//字典类型
        }
        public void put(K key,V value){
            storage.put(key,value);
        }
        public V get(K key){
            return storage.get(key);
        }
        public V remove(K key){
            return storage.remove(key);
        }
        public int size(){
            return storage.size();
        }
        public boolean isEMpty(){
            return storage.isEmpty();
        }
    }
}