Binary to Decimal Number

/* Using loops write a program that converts a binary integer number to its decimal form.
 * The input is entered as string. The output should be a variable of type long. */

import java.util.Scanner;

public class _13_BinaryToDecimalNumber {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner scan = new Scanner(System.in);
        System.out.print("Enter your Binary number on single line, without spaces: ");
        String binaryStr = scan.next();
        scan.close();

        // The Short way:
        // long decNum = Long.parseLong(binaryStr, 2);

        long decNum = convertBinaryNumberToDecimalNumber(binaryStr);

        System.out.println("That Binary number in Decimal system is: " + decNum);
    }

    private static long convertBinaryNumberToDecimalNumber(String binary) {
        // TODO Auto-generated method stub
        long sum = 0;
        long multiplier = 1;
        for (int i = binary.length() - 1; i >= 0; i--) {
            int digit = Integer.parseInt("" + binary.charAt(i));
            sum += digit * multiplier;
            multiplier *= 2;
        }

        return sum;
    }

}