Solution #1 Using Recursion public static int fibonacciRecursion(int nthNumber) { //use recursion if (nthNumber == 0) { return 0; } else if (nthNumber == 1) { return 1; } return fibonacciRecursion(nthNumber - 1) + fibonacciRecursion(nthNumber - 2); } Solution #2 Using Iteration public static int fibonacciLoop(int nthNumber) { //use loop int previouspreviousNumber, previousNumber = 0, currentNumber = 1; for (int i = 1; i < nthNumber ; i++) { previouspreviousNumber = previousNumber; previousNumber = currentNumber; currentNumber = previouspreviousNumber + previousNumber; } return currentNumber; }