How can I find the sum of two numbers which are in String variables?

Question

In this code fragment, I can\'t sum a and b:

String a = \"10\";
String b = \"20\"; 
JOptionPane.showMessageDialog(null,a+b);
         


        

Answer 1

We can change string to BigInteger and then sum its values.

import java.util.*;
import java.math.*;
class stack
{
    public static void main(String args[])
    {
        Scanner s=new Scanner(System.in); 
        String aa=s.next();
        String bb=s.next();
        BigInteger a=new BigInteger(aa);
        BigInteger b=new BigInteger(bb);
        System.out.println(a.add(b));
    }
}