编写程序，求n!。 编写程序，求1!+3!+5!+7!+9!。

以下是两种Java求阶乘的例子：
1. 普通方法

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int sum = 0;
        int fac = 1;
        for (int i = 1; i <= n; i++) {
            fac *= i;
            sum += fac;
        }
        System.out.println(sum);
    }
}

2. 递归方法

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);        int n = sc.nextInt();
        int sum = 0;
        for (int i = 1; i <= n; i += 2) {
            sum += factorial(i);
        }
        System.out.println(sum);
    }

    public static int factorial(int n) {
        if (n == 1) {
            return 1;
        } else {
            return n * factorial(n - 1);
        }
    }
}

以下是Java求1!+3!+5!+7!+9!的例子：

public class Main {
    public static void main(String[] args) {
        int sum = 0;
        for (int i = 1; i <= 9; i += 2) {
            sum += factorial(i);
        }
        System.out.println(sum);
    }

    public static int factorial(int n) {
        if (n == 1) {
            return 1;
        } else {
            return n * factorial(n - 1);
        }
    }
}