Java Iterative Fibonacci (long) Code Example

 

package gigasblade;

// If you have any comments and/or suggestions, please let me know!
public class FibonacciIterative {
    private static long fibonacci(long n) {
        if (n <= 0)
            throw new IllegalArgumentException();
        if (n <= 2) {
            return 1;
        }
        int an1 = 1, an2 = 1;
        int an = an1 + an2;
        for (int i = 3; i <= n ; i++) {
            an1 = an2;
            an2 = an;
            an = an1+an2;
        }
        return an;
    }

    private static void checkFibonacci(long n) {
        try {
            System.out.println("fibonacci(" + n + "): " + fibonacci(n));
        } catch (IllegalArgumentException e) {
            System.err.println("fibonacci(" + n + "): " + e);
        }
    }

    public static void main(String[] args) {
        for (int n = -2 ; n <= 18; n++) {
            checkFibonacci(n);
        }
    }
}

fibonacci(-2): java.lang.IllegalArgumentException
fibonacci(-1): java.lang.IllegalArgumentException
fibonacci(0): java.lang.IllegalArgumentException
fibonacci(1): 1
fibonacci(2): 1
fibonacci(3): 3
fibonacci(4): 5
fibonacci(5): 8
fibonacci(6): 13
fibonacci(7): 21
fibonacci(8): 34
fibonacci(9): 55
fibonacci(10): 89
fibonacci(11): 144
fibonacci(12): 233
fibonacci(13): 377
fibonacci(14): 610
fibonacci(15): 987
fibonacci(16): 1597
fibonacci(17): 2584
fibonacci(18): 4181

Process finished with exit code 0