Problem 16: Power digit sum

2¹⁵ = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 2¹⁰⁰⁰?

Solution:
Again I've used BigInteger because 2¹⁰⁰⁰  doesn't fit inside long.
Here's the java code

import java.math.BigInteger;


public class Prob16 {

 
 public static void main(String[] args) {
int sum =0;
int digit;
  BigInteger a = new BigInteger("1");
  BigInteger b = new BigInteger("2");
for(int i = 1 ; i <= 1000 ; i++ )
{
 a = a.multiply(b);
}
String A = a.toString();

for(int i =0 ; i < A.length();i++)
{
  digit = A.charAt(i) - '0'; 
 sum = sum + digit;
}
System.out.println(sum);
 }
}