递归笔试题

笔试题：第1个人10，第2个比第1个人大2岁，依次递推，请用递归方式计算出第8个人多大？

下面是我的实现方法

class Algorithm {private static Algorithm instance;private Algorithm(){}public int computeAge(int n) throws IllegalAccessException {if(n < 1)throw new IllegalAccessException();if(n == 1) {return 10;}return computeAge(n -1) + 2;}public static synchronized Algorithm  getInstance() {if(instance == null) {instance = new Algorithm();}return instance;}}public class Main {public static void main(String[] args) throws IllegalAccessException {Algorithm algorithm = Algorithm.getInstance();System.out.println(algorithm.computeAge(100));}}