swap three variables in java without using temporary variable

public class SwapThreeNumbersWithoutTemp
{
   static int num1, num2, num3;
   public static void main(String[] args) 
   {
      num1 = 30; num2 = 60; num3 = 90; 
      System.out.println("Before swapping three numbers: num1 = " + num1 + ", num2 = " + num2 + ", num3 = " + num3);
      swapWithoutTemporary();
      System.out.println("After swapping three numbers: num1 = " + num1 + ", num2 = " + num2 + ", num3 = " + num3);
   }
   static void swapWithoutTemporary() 
   { 
      num1 = num1 + num2 + num3; 
      num2 = num1 - (num2 + num3); 
      num3 = num1 - (num2 + num3); 
      num1 = num1 - (num2 + num3);  
   }
}