Object-Oriented Programming with Java, part I – Exercise 35

This code calculates the sum of the series 2^0 + 2^1 +….2^n where n is a number input by the user.

My Code

import java.util.Scanner;

public class SumOfThePowers {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        System.out.print("Type a number: ");
        int inputNum = Integer.parseInt(reader.nextLine());
        int tick = 0;
        int result = 0;
        while (tick <= inputNum){
            result += (int)Math.pow(2, tick);
        System.out.println("The result is " + result);

Model Code


I think I did fairly well on this one. I had a couple of problems. My code was refused as I hadn’t converted the double output by Math.pow(2, tick) back into an integer and I spent quite a while trying to figure out why it didn’t work only to find that I have used =+ instead of +=. For some reason this makes a difference.

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