计算斐波那契数列第n项值的方法

public class Demo {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int n = scan.nextInt();
System.out.println(f(n));

}

public static long f(int n){

Scanner scan = new Scanner(System.in);

 

//数列第一项和第二项是1

if(n==1||n==2){
return 1;
}
while(n<1){
System.out.println("输入错误");
n = scan.nextInt();

}

long[] arr = new long
;
arr[0] = 1;
arr[1] = 1;
for (int i = 2; i < arr.length; i++) {
arr[i] = arr[i-1]+arr[i-2];
}
return arr[n-1];

}

}