Power Digit Sum

PowerDigitSum.java

import java.math.BigInteger; // header stuff MUST go above the first class

// our main class becomes a file but the main method is still found
public class PowerDigitSum
{
  public static void main(String[] args)
  {
    BigInteger bigPow = pow(2, 1000);
    
    System.out.println("power: " + bigPow);
    
    String str = bigPow.toString();
    
    System.out.println("string length: " + str.length());
    
    long sum = 0;
    for (int i = 0; i < str.length(); i++){
      sum += Long.valueOf(Character.getNumericValue(str.charAt(i)));
    }
    
    System.out.println("sum: " + sum);
   
  }
  
  public static BigInteger pow(long x, long n){
    long mid;
    BigInteger temp = BigInteger.ZERO;
    if (n == 0){
      return BigInteger.ONE;
    }
    if (n == 1){
      return BigInteger.valueOf(x);
    }

    mid = n / 2;
    temp = pow(x, mid);

    if (n%2 == 0){
      return (temp.multiply(temp));
    }
    else{
      return (BigInteger.valueOf(x).multiply(temp).multiply(temp));
    }

  }
  
}

/*output:

power: 10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376
string length: 302
sum: 1366


*/


//Another implementation:

import java.math.BigInteger;

public class euler16 {
	public static void main(String[] args) {
		BigInteger b1,b2;
		b1=  BigInteger.valueOf(1);
		b2= BigInteger.valueOf(2);
		for (int i=0;i<1000 ;i++ ) {
			b1=b1.multiply(b2);			
		}
		String s= null;
		s= b1.toString(10);
		int sum=0;
		for (int j=0;j<s.length() ;j++ ) {
			sum=sum+((int)s.charAt(j)-48);
		}
		System.out.println(sum);
	}
}


//And another:

import java.math.BigInteger; 


public class PowerDigitSum {

    public static void main(String[] args) {

        BigInteger bint = new BigInteger("2");
        bint = bint.pow(1000);
        String x = bint.toString();
        long sum = 0;
        for (int i = 0; i < x.length(); i++) {
            sum  += Integer.parseInt(x.substring(i, i + 1));
        }
        System.out.println(sum);
    }
}