public class Demo01 {
    public static void main(String args[]) {
        for (int i = 1; i <= 20; i++)
            System.out.println(f(i));
    }
    public static int f(int x) {
        if (x == 1||x == 2)
            return 1;
        else
            return f(x - 1) + f(x - 2);
    }
}

还有一种

public class fr {
    public static void main(String[] args) {
        demo s=new demo();
        for(int i=1;i<=20;i++) {
            System.out.println(s.tuzi(vb ));
        }
    }
}
class demo{
    public int tuzi(int i) {
        if(i==1||i==2) {
            return 1;
        }else {
            return tuzi(i-1)+tuzi(i-2);
        }
    }
}