【Java】求大数阶乘

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    // 计算 n 的阶乘
    public static BigInteger factorial(int n) {
        BigInteger result = BigInteger.ONE;
        
        for (int i = 2; i <= n; i++) {
            result = result.multiply(BigInteger.valueOf(i));
        }
        
        return result;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入一个正整数 n: ");
        int n = scanner.nextInt();

        // 检查输入是否有效
        if (n < 0) {
            System.out.println("负数没有阶乘！");
        } else {
            BigInteger result = factorial(n);
            System.out.printf("%d 的阶乘是: %s%n", n, result);
        }
        
        scanner.close();
    }
}