http://xeyez.nflint.com/wiki/index.php?title=Recursion

	public static int sum(int n) {
		if(n <= 0)
			return n;
		
		return n + sum(n - 1);
	}

	private static int factorial(int n) {
		if(n == 0) //0! = 1
			return 1;
		else
			return n * factorial(n-1);
	}

	public static int fibonacci(int n) {
		if(n < 1)
			throw new StackOverflowError("1보다 커야 합니다.");
		
		if(n == 1) {
			return 0;
		}
		else if (n == 2) {
			return 1;
		}
		else {
			return fibonacci(n - 1) + fibonacci(n - 2);
		}
	}

	public static void hanoiTower(int n, String from, String to, String temp) {
		if(n == 1) {
			System.out.println(String.format("원반 %d개 %s → %s", n, from, temp));
		}
		else {
			hanoiTower(n - 1, from, temp, to);
			System.out.println(String.format("원반 %d개 %s → %s", n, from, temp));
			
			hanoiTower(n - 1, temp, from, to);
		}
	}