Java:
将代码组织成函数

public class MathUtils {

    public static void main(String[] args) {
        int number = 5;
        int result = factorial(number);
        System.out.println("数字 " + number + " 的阶乘是: " + result);
    }
    
    public static int factorial(int n) {
        if (n <= 1) {
            return 1;
        }
        return n * factorial(n - 1);
    }
}