OddEvenSum.java

public class OddEvenSum {

    public static void main(String[] args) {

        final int LOWERBOUND = 0;
        final int UPPERBOUND = 1000;

        int sumOdd = 0;
        int sumEven = 0;

        int number = LOWERBOUND;

        while (number <= UPPERBOUND) {

            if (number % 2 == 0) {
                sumEven += number; // Same as sumEven = sumEven + number
            } else {
                sumOdd += number;
            }
            ++number;
        }
        System.out.println("The sum of odd numbers from " + LOWERBOUND + " to " + UPPERBOUND + " is " + sumOdd);
        System.out.println("The sum of even numbers from " + LOWERBOUND + " to " + UPPERBOUND + "  is " + sumEven);
        System.out.println("The difference between the two sums is " + (sumOdd - sumEven));
    }

}