public class ConvertStrToNum
{
    public static void main(String[] args)
    {
        int i;
        double x;
        String s;
        
        s = "123"; // Cannot be used in calculation 
        i = Integer.parseInt(s); // Convert num str to int
        i = i + 1;               // Now can be used in calc
        
        s = "3.14"; // Cannot be used in calculation
        x = Double.parseDouble(s); // Convert num str to DOuble
        x = x + 1;                 // Now can be used in calc

        // i = Integer.parseInt("3.14");
    }
}