Calculate Swap The Two Numbers Using Java

            /*  SWAP THE TWO NUMBERS    */

import java.io.*;
import java.text.*;

class ssva20
{
    public static void main(String arg[]) throws IOException
    {
        BufferedReader obj=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("\n     SWAP TWO NUMBERS");
        System.out.println("     ---- --- -------");
        System.out.println("\n\tI N P U T");
        System.out.println("\t- - - - -");
        System.out.print("\n ENTER THE FIRST NUMBER (M) : ");
        double m=Double.parseDouble(obj.readLine());
        System.out.print("\nENTER THE SECOND NUMBER (N) : ");
        double n=Double.parseDouble(obj.readLine());
        NumberFormat nf=NumberFormat.getInstance();
        nf.setMinimumFractionDigits(2);
        m=m+n;
        n=m-n;
        m=m-n;
        System.out.println("\n\tO U T P U T");
        System.out.println("\t- - - - - -");
        System.out.println("\n THE SWAP OF FIRST NUMBER (M) IS : "+nf.format(m));
        System.out.println("\nTHE SWAP OF SECOND NUMBER (N) IS : "+nf.format(n));
        System.out.println("\n\n");
    }
}