public class Pair {
     private Object key;
     private Object value;
     public Pair(Object key, Object value) {
         this.key = key;
         this.value = value;
     }
     //交换键值
     public Pair swap(){
         return new Pair(value,key);
     }
     public Object getKey(){
         return key;
     }
     public Object getValue(){
         return value;
     }
     @Override
     public String toString() {
         return "键："+key+"  值："+value;
     }
     public static void main(String[] args) {
         Pair p1 = new Pair("姓名","张三");
         System.out.println("交换前："+p1);
         Pair p2 = p1.swap();
         System.out.println("交换后："+p2);
     }
 }