Question

Write a java program to print all the powers of 2 below a certain number and calculate their sum

Requirements:

1. Accept the upper limit from the user as an integer

2. Make sure the sum variable is of the “long” type. You can assume that the test output will be less than LONG MAX.

3. Print all the numbers as a running sum, and finally print their sum.

Please try and restrict yourself to loops, selection statements, and calls to library methods

Example Run:

Enter the upper limit: 500

1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 = 511

Answer 1

import java.util.Scanner;

public class SumPowers2 {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter the upper limit: ");
        int max = in.nextInt();
        int sum = 1, n = 1;
        System.out.print("1");
        while (n*2 <= max) {
            n *= 2;
            sum += n;
            System.out.print(" + " + n);
        }
        System.out.println(" = " + sum);
    }
}

Enter the upper limit: 500 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 = 511 Process finished with exit code 0,