swapping without third variable in java code example

Example 1: swap three variables in java without using temporary variable

// 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);  
   }
}

Example 2: swap 2 integers without using temporary variable

using System;

class MainClass {
  public static void Main (string[] args) {
    int num1 = int.Parse(Console.ReadLine());
    int num2 = int.Parse(Console.ReadLine());
      num1 = num1 + num2; 
      num2 = num1 - num2; 
      num1 = num1 - num2; 
      Console.WriteLine("After swapping: num1 = "+ num1 + ", num2 = " + num2); 
    Console.ReadLine();
  }
}

Example 3: swapping values in java using a function not working

#include <stdio.h>

int main() {
   int a = 23, b = 47;
   int t;
   printf("Before. a: %d, b: %d\n", a, b);
   t = a;
   a = b;
   b = t;
   printf("After.  a: %d, b: %d\n", a, b);
   return 0;
}