Java Program:

Example:

import java.util.Scanner;
public class SwapProgram {
  public static void main(String []args) {
    int n1,n2;
    Scanner userInput = new Scanner(System.in);
    System.out.print("Enter 1st number : ");
    n1 = userInput.nextInt();
    System.out.print("Enter 2nd number : ");
    n2 = userInput.nextInt();

    n1=n1+n2;
    n2=n1-n2;
    n1=n1-n2;
    System.out.println("After Swapping\n Value of 1st number :"+ n1 
    + "\n Value of 2nd number : " + n2);
  }
}

Output:

  Enter 1st number : 7
  Enter 2nd number : 15
  After Swap
  1st number : 15
  2nd number : 7

Here we are adding both values into one then used some maths

//Lets take n1=7, n2=3;

n1=n1+n2; //n1=7+3=10
n2=n1-n2; //n2=10-3=7
n1=n1-n2; //n1=10-7=3

//Finally you swaped & get n1=3, n2=7;