java方法的調用中形參和實參的值傳遞

public class MethodExample1
{
  	int n1,n2;       //定義成員變量n1,n2

 	 public void swap_value(int n1,int n2)  //定義成員方法帶兩個整型參數
  	{//按值傳遞
  		int n0;     //定義方法變量n0,
  		n0=n1;    //先將n1的值賦給n0
  		n1=n2;    //再將n2的值賦給n1
  		n2=n0;   //最后將n0 (原n1) 的值賦給n2
  		System.out.println("在方法swap_value中:n1="+n1+"; n2="+n2);
 	 }
 	 
 	public void swap(MethodExample1 n)
  	{//按引用傳遞
  		int n0;     //借助方法變量n0,交換成員變量n1,n2的值
  		n0=n.n1;
  		n.n1=n.n2;
  		n.n2=n0;
  		System.out.println("在方法swap中:n.n1="+n.n1+"; n.n2=" +n.n2);
  	} 
 	public static void main(String [] arg) //以下定義main()方法
 	{
		int  n1=1,n2=10;   //定義方法變量
    	MethodExample1 numbers=new MethodExample1();  //生成本類對象
    	numbers.swap_value(n1,n2); //變量n1,n2的值為實參調用swap_value
   		System.out.println("在main()方法中:n1="+n1+" n2="+n2);
   		numbers.n1=5;    //為對象的成員變量n.n1賦值
   		numbers.n2=20;   //為對象的成員變量n.n2賦值
   		numbers.swap(numbers);  //以對象numbers為實參調用方法swap
   		System.out.println("在main()方法中:numbers.n1="+numbers.n1+" numbers.n2="+numbers.n2);
  	}
}