Complex Equation Loop Question

Question

The code i have so far is
class MainApplication {
     public static void main(String args[]) {
          MathLib math = new MathLib();
          math.sumOfNumbers(2);
          math.sumOfNumbers(10);
          math.sumOfNumbers(200);
class MathLib {
     public void sumOfNumbers(int num) {
               int sum = 0;
               // put the loop in here
               System.out.println("sum = " + sum);
What you need to do is put a loop inside the sumOfNumbers() to calculate the sum of all numbers from 0 to the parameter passed.
For example, if the parameter is 2, the calculation is: 0+1+2 = 3.
For example, if the parameter is 3, the calculation is: 0+1+2+3 = 6.
For example, if the parameter is 4, the calculation is: 0+1+2+3+4 = 10.
and so on
I found a site http://mathforum.org/library/drmath/view/57919.html to help but couldnt figure it out.
I only need to modify the Mathlib class.
Im trying to get it to print out
sum = 3
sum = 55
sum = 20100

Answer 1

public class GaussLives
    public void sumOfNumbers(int num)
        System.out.println((num * (num + 1)) / 2);
    public static void main(String[] args)
        GaussLives gaussLives = new GaussLives();
        for (int i = 0; i < 20; i++)
            gaussLives.sumOfNumbers(i);
        gaussLives.sumOfNumbers(100);
}