java学习p220

import java.util.Scanner;
public class a1 {
    public static void main(String[] args) {
        Scanner myScanner = new Scanner(System.in);
        System.out.println("请输入斐波那契数列的项数");
        int n = myScanner.nextInt();
        tools t1 = new tools();
        int term = t1.fibonacci(n);
        if (term == -1) {
            System.out.println("输入错误");
        }
        else {
            System.out.println("斐波那契数列第" + n + "个项为 " + term);
        }
    }
}
class tools {
    public int fibonacci(int n) {
        if (n < 0) {
            return -1;
        }
        else if (n == 0) {
            return 0;
        }
        else if (n == 1 || n == 2) {
            return 1;
        }
        else {
            return fibonacci(n - 1) + fibonacci(n - 2);
        }
    }
}