need help with loops plz

[Nim]

The method you have is about as simple and as elegant as it gets.

Inefficiency isn't elegant.

Don't use recursion for the Fibonacci sequence. It's running time is exponential --(3/2)^N. Every CS book that has a chapter on algorithmic analysis tells you this.

public class Test {
	private final static int N = 40;
	public static void main(String[] args) {
		long start = System.currentTimeMillis();
		int a = 0, b = 1, c = 1;
		for (int i = 4; i <= N; i++) {	// i = 4 -> 5 -> 6 -> 7 ...
			a = b;			// a = 1    1    2    3
			b = c;			// b = 1    2    3    5
			c = a + b;		// c = 2    3    5    8
		}
		long end = System.currentTimeMillis();
		
		System.out.println("f_" + N + " = " + c + " and iteratively took " +
			(end - start) + " milliseconds.");
		
		
		start = System.currentTimeMillis();
		c = fib(N);
		end = System.currentTimeMillis();
		
		System.out.print("f_" + N + " = " + c + " and recursively took " +
			(end - start) + " milliseconds.");
	}
	private static int fib(int n) {
		if (n <= 3)
			return 1;
		return fib(n - 1) + fib (n - 2);
	}
}

Output:

f_30 = 514229 and iteratively took 0 milliseconds.
f_30 = 514229 and recursively took 16 milliseconds.

f_40 = 63245986 and iteratively took 0 milliseconds.
f_40 = 63245986 and recursively took 672 milliseconds.

f_50 = -811192543 and iteratively took 0 milliseconds.     (longs obv. don't work well with big N)
f_50 = -811192543 and recursively took 77359 milliseconds. (1 minute 17.359 seconds...)