swapping of two numbers in java with temporary variable

1public class Exercise15 {
2  public static void main(String[] args) {
3     // int, double, float
4   int a, b;
5   a = 15;
6   b = 27;
7   System.out.println("Before swapping : a, b = "+a+", "+ + b);
8   a = a + b;
9   b = a - b;
10   a = a - b;
11   System.out.println("After swapping : a, b = "+a+", "+ + b);
12 }
13 
14}
15
16

1public class Main{public static void main(String[] args) {float a = 3.66f, b = 6.47f;System.out.println("a number " + a);System.out.println("b number " + b);float temp = a;a = b;b = temp;System.out.println("After swapping");System.out.println("a number " + a);System.out.println("b number " + b);}}

1// swap three variables in java without using temporary variable
2public class SwapThreeNumbersWithoutTemp
3{
4   static int num1, num2, num3;
5   public static void main(String[] args) 
6   {
7      num1 = 30; num2 = 60; num3 = 90; 
8      System.out.println("Before swapping three numbers: num1 = " + num1 + ", num2 = " + num2 + ", num3 = " + num3);
9      swapWithoutTemporary();
10      System.out.println("After swapping three numbers: num1 = " + num1 + ", num2 = " + num2 + ", num3 = " + num3);
11   }
12   static void swapWithoutTemporary() 
13   { 
14      num1 = num1 + num2 + num3; 
15      num2 = num1 - (num2 + num3); 
16      num3 = num1 - (num2 + num3); 
17      num1 = num1 - (num2 + num3);  
18   }
19}