How can I swap the values of two ints in the method of Java?

Question

In Java, it seems that the primitive data type arguments will pass into the method by value. But what if I want to swap the values of two integers.

public static void main(String[] args){
   int a = 1;
   int b = 2;
   swapvalue(a,b);
   System.out.println(a);
   System.out.println(b);    
}

public static void swapValue(int a, int b){
   int c = a;
   a = b;
   b = c;
}

For example, the code above is aimed to swap the values of a and b. In C++ I can pass into the pointers or references to them but I have no idea about how to do this in Java without pointers. How could I make it?

Answer 1

You can't swap them by passing them to a method.

The closest thing you can do is pass an int[] to the method, and swap the elements of the array :

public static void main(String[] args){
   int[] arr = {1,2};
   swapValues(arr);
   System.out.println(arr[0]);
   System.out.println(arr[1]);    
}

public static void swapValues(int[] arr){
   int c = arr[0];
   arr[0] = arr[1];
   arr[1] = c;
}

Another alternative is to wrap them with some mutable class :

public class IntHolder
{
    private int value;
    ...
}

public static void main(String[] args){
   IntHolder a = new IntHolder(1);
   IntHolder b = new IntHolder(2);
   swapValue(a,b);
   System.out.println(a.getInt());
   System.out.println(b.getInt());    
}

public static void swapValue(IntHolder a, IntHolder b){
   int c = a.getInt();
   a.setInt(b.getInt());
   b.setInt(c);
}