TriangluarStars4

/*A “star number”, s, is a number defined by the formula:  s = 6n(n-1) + 1  where n is the index
 *of the star number. Thus the star numbers are:   1, 13, 37, 73, 121, 181, 253, …
 *A “triangle number”, t, is the sum of the numbers from 1 to n:   t = 1 + 2 + … + (n-1) + n.
 *Thus the triangle numbers are:  1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136,
 *153, 171, 190, 210, 231, 253, …
 *Write a Java application that produces a list of all the values of type int that are simultaneously
 *star numbers and triangle numbers.  As part of this problem you must write and use the following functions:
 *      An isStarNumber() routine which determines if the passed number is a star number or not.
 *      A determineStarNumber() function which returns the star number of a passed index (i.e. value of n).
 */
public class TriangularStars {

    public static int currentNumber = 0;
    public static int previousNumber = 0;
        public static void main(String[] args) {


            System.out.println("The following are numbers which are both triangle numbers and star numbers: ");
            int previousTriangleNumber=0;
            int currentTriangleNumber=0;
            int index=1;
            while (currentNumber>=previousNumber)
            {
                currentTriangleNumber = previousTriangleNumber + index;
                //System.out.println(currentTriangleNumber);
                previousNumber = currentNumber;
                if (isStarNumber(currentTriangleNumber))
                {
                    System.out.print(currentTriangleNumber + ", ");

                }
                currentNumber = currentTriangleNumber;
                previousTriangleNumber = currentTriangleNumber;
                index++;
            }

        }

        public static boolean isStarNumber (int number)
        {

            boolean isStarNumber = false;
            int index = 0;
            int currentStarNumber = 0;
            int previousStarNumber = 0;

            while (!isStarNumber && currentStarNumber <= number )
            {
                previousStarNumber = currentStarNumber;
                currentStarNumber = determineStarNumber(index);
                //System.out.println(currentStarNumber + "; " + previousStarNumber);
            /*    if (currentStarNumber < previousStarNumber)
                {
                    isStarNumber = false;
                    System.out.println(currentStarNumber);
                    System.out.print("; " + index);
                }*/
                if (currentStarNumber == number)
                {
                    isStarNumber = true;
                }
                else
                    index += 1;
                }

            return (isStarNumber);
        }

        public static int determineStarNumber (int index)
        {
            /*int starNumberValue = 0;
            if (1 <= ((6*index)/Integer.MAX_VALUE) && 1 <= ((6*index) * (index-1)/Integer.MAX_VALUE))
            {
                starNumberValue = (6*index) * (index-1) + 1;
            }
            else
                starNumberValue = -1;
                */
            int starNumberValue = (6*index) * (index-1) + 1;
            return (starNumberValue);

        }

}