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

Since + is used to concat strings, you can't use it to add two strings containing number. But subtraction works perfectly fine with such strings. Hence, you can use this basic mathematical concept to make that possible:

a-(-b)