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

use BigInteger class to perform largely in length string addition operation.

BigInteger big = new BigInteger("77777777777777777777888888888888888888888888888856666666666666666666666666666666");
        BigInteger big1 = new BigInteger("99999999999999995455555555555555556");
        BigInteger big3 =   big.add(big1);