OK. If I really want to pass by reference, How can I do

Question

I want to write a method called
public void swap(int a, int b){
public static void main(String[] args){
int a=1;
int b=2;
swap(a, b);
System.out.print(a);
System.out.print(b);
And I want the output to be 21, how can I achieve this in Java?
Thanks!

Answer 1

You can achieve the same effect that you're after, just not exactly the way you're attempting to - you just need to define a class as a data structure to hold your int values.
class IntHolder
          public int a;
          public int b;
}Then pass an object instance of your class to the swap method.
     public static void main(String[] args)
          IntHolder nums = new IntHolder();
          nums.a = 1;
          nums.b = 2;
          System.out.println("Main - before");
          System.out.print(nums.a);
          System.out.print(nums.b);
          swap(nums);
          System.out.println("Main - after");
          System.out.print(nums.a);
          System.out.print(nums.b);
     static void swap(IntHolder ih)
          Integer tmp;
          tmp = ih.a;
          ih.a=ih.b;
          ih.b=tmp;
          System.out.println("In Swap");
          System.out.print(ih.a);
          System.out.print(ih.b);
     }