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 void setKey(K key){
        this.key=key;
    }
    public void setValue(V value){
        this.value=value;
    }
    public Pair<V,K> swap(){
        return new Pair<>(value,key);
    }
    @Override
    public String toString(){
        return "("+key+","+value+")";
    }
    public static void main (String []args){
        Pair<String,Integer> pair=new Pair<>("小红",18);
        System.out.println("交换前:"+pair);
        Pair<Integer,String> swapped=pair.swap();
        System.out.println("交换后:"+swapped);
    }
}