我正在编写一个程序，使用Ramanujan级数来估计pi。在这个系列中，它需要我计算几个表达式的阶乘，我为此编写了一个类。我在之前的作业中使用了这个类，解释了类顶部的测试。当我试图创建阶乘对象来使用Factorial.calculate(nthNum)时，我的问题开始发挥作用。我已经尝试了我能想到的一切，搜索了许多论坛，回顾了我的笔记，我不明白为什么这个错误不断发生。

.\Ramanujan.java:9: error: cannot find symbol
        Factorial f = new Factorial();
        ^
  symbol:   class Factorial
  location: class Ramanujan
.\Ramanujan.java:9: error: cannot find symbol
        Factorial f = new Factorial();
                          ^
  symbol:   class Factorial
  location: class Ramanujan
2 errors
error: compilation failed

如果有人能向我解释为什么找不到这个符号，那将是非常有帮助的。谢谢。

public class Ramanujan {
    public static void main (String[] args){
        String nthRamNumString = args[0];
        int nthRamNum = Integer.parseInt(nthRamNumString);
        findRamNum(nthRamNum);
    }

    public static double findRamNum(int nthNum){
        Factorial f = new Factorial();
        double factNum = f.calculate(nthNum);
        double firstVal = ((2 * Math.sqrt(2)) / 9801);
        double piNum = 0;
        for (int i = 0; i <= nthNum; i++){
            piNum = piNum + (4 * factNum) * (1103 + (26390 * nthNum)) / 
            (Math.pow(factNum, 4) * (Math.pow(396, 4 * nthNum)));
        }
        double finalPiVal = (firstVal * piNum);
        return 1 / finalPiVal;
    }
}

public class Factorial {
    public static void main (String[] args){
        String value = args[0];
        Long n = Long.parseLong(value);
        if (n > 20){
            System.out.println("Value must be less than 20!");
            System.exit(0);
        }
        else if (n < 0){
            System.out.println("Value must be greater than 1!");
            System.exit(0);
        }
        else{
            System.out.println(calculate(n));
        }
        Long result = calculate(0);
        if (result == 1){
            System.out.println("Factorio.calculate(0) returned " + result + ". Test passed!");
        }
        else{
            System.out.println("Factorio.calculate(0) returned " + result + ". Test failed!");
        }
        result = calculate(5);
        if (result == 120){
            System.out.print("Factorio.calculate(5) returned " + result + ". Test passed!");
        }
        else{
            System.out.print("Factorio.calculate(5) returned " + result + ". Test failed!");
        }
    }

    public static long calculate(long n){
        long factNum = 0;
        if (n == 0){
            return 1;
        }
        else{
            for (int i = 0; i <= n; i++){
                factNum = factNum + (n * (n - 1));
            }
        }
        return factNum;
    }
}