Computer Science 202
Introduction to Programming

Fall 2012, The College of Saint Rose

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Sum2ToNBy2 BlueJ Project

Click here to download a BlueJ project for Sum2ToNBy2.

Sum2ToNBy2 Source Code

The Java source code for Sum2ToNBy2 is below. Click on a file name to download it.

Sum2ToNBy2.java

/*
 * Example Sum2ToNBy2: sum the even integers from 2 to some specified upper limt
 *
 * Jim Teresco, The College of Saint Rose, CSC 202, Fall 2012
 *
 * $Id: Sum2ToNBy2.java 1937 2012-10-08 18:06:13Z terescoj $
 */

import java.util.Scanner;

public class Sum2ToNBy2 {

    public static void main(String[] args) {

        // we'll read the upper limit from the keyboard
        Scanner keyboard = new Scanner(System.in);

        // the upper limit should be an even number greater than 0
        int upperLimit = 0;
        while (upperLimit <= 0 || upperLimit % 2 != 0) {

            System.out.print("Enter an even positive integer for the upper limit of our sum: ");
            upperLimit = keyboard.nextInt();

            if (upperLimit <= 0) {
                System.out.println("Make it positive!");
            }
            else if (upperLimit % 2 != 0) {
                System.out.println("Make it even!");
            }
        }

        // now we are ready to compute the sum
        // initialize to 0 to start
        int sum = 0;

        // count by 2's up to our limit:
        // notice we are initializing our number to 2, we continue
        // as long as number is less than or equal to the 
        // upper limit, and we add 2 to the number each time around
        // using our += shorthand notation for number = number + 2
        for (int number = 2; number <= upperLimit; number += 2) {

            // shorthand to add number to sum
            sum += number;
        }

        // and print our result
        System.out.println("Our sum is " + sum);

    }
}