example for http://stackoverflow.com/q/39339015/1281433

public class IterativeSummer {
    /**
     * Returns a sum, computed iteratively.
     *
     * @param x the augend
     * @param y the addend
     * @return the sum of the augend and addend
     */
    public int iterativeSumDriver(int x, int y) {
        int[] result = iterativeSumInternal(x,y);
        while (result.length == 2) {
            result = iterativeSumInternal(result[0], result[1]);
        }
        return result[0];
    }

    /**
     * Returns the new computation state of a iterative sum
     * computation.  If x is 0, then returns an array of just y.
     * Otherwise, returns an an array of x-1 and y+1.
     *
     * @param x the augend
     * @param y the addend
     * @return the next interal state
     */
    int[] iterativeSumInternal(int x, int y) {
        if (x == 0) {
            return new int[] { y };
        }
        else {
            return new int[] { x-1, y+1 };
        }
    }

    public static void main(String[] args) {
        int x = 5;
        int y = 6;
        int sum = new IterativeSummer().iterativeSumDriver(x,y);
        System.out.println(String.format("%d + %d = %d", x, y, sum));
    }
}