Swapping A and B without 3rd variable

So my teacher gave me a task, a simple task to swap two values in our new Java class. That was an easy task as we had a good background in the Programming language. But he stated that no more than two elements were allowed. That seems a tricky one and everyone in the class was clueless cause this was the mathematical approach for solving.
So it was a bit confusing and after finding a solution I was a bit surprised as there was indeed a better technique for swapping.
steps
* add a and b and assign to a
* subtract a from b and assign to b
* subtract a from b and assign to a
Now, this became our simple swapping without using the third parameter.
Here is a code in java.

class SwapTest {

  public static void main(String arg[]) {
    int a = 999999999;

    int b = 999999999;
    a = a + b;
    b = a - b;
    a = a - b;
    System.out.println("a=" + a + " b=" + b);
  }
}

disadvantage of this method in java is that while using integer it will overflow when the number is large

Comments

[Aleatório]

You can do the same with XOR operator and without the problem of overflow:

class SwapTest {

  public static void main(String arg[]) {
    int a = 1;
    int b = 2;

    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
    System.out.println("a=" + a + " b=" + b);
  }
}

[yubaraj singh]

wow, thanks for that trick.