BigInteger难度大 [英] Difficulty with BigInteger

问题描述

我正在尝试使用Recursion和BigIntegers进行Factorial，但eclipse正在抱怨BigInteger。我知道这个程序本来应该很简单，但它给我带来了麻烦。这是代码。

I am trying to do Factorial with Recursion and BigIntegers but eclipse is complaining about the BigInteger. I know the program is supposed to be simple but it is giving me headache. Here is the code.

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

public class Factorial
{
    public static void main(String[] args) 
    {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter integer");
        BigInteger n = input.nextBigInteger();
        System.out.println("Factorial of " + n + " is "  + fact(n));

    }

    public static  int fact(BigInteger n)
    {
        if(n ==0)
        {
            return 1;
        }
        else
        {
            return n * fact(n-1);
        }
    }
}

推荐答案

BigInteger 不支持使用 == 进行比较，并使用进行乘法* 。相反，您必须调用 BigInteger 类的相应方法（ equals（） 和 multipy（） ）。

BigInteger does not support comparison using == and multiplication using *. Instead, you have to call the appropriate methods of the BigInteger class (equals() and multipy()).

另请注意，存在 BigInteger.ZERO 和 BigInteger.ONE 。

Also note that there exist BigInteger.ZERO and BigInteger.ONE.

最后， fact 方法的返回类型应该是 BigInteger 而不是 INT 。是否希望参数的类型为 BigInteger 或 int 由您决定。

Finally, the return type of your fact method should be BigInteger and not int. Whether you want the argument to be of type BigInteger or int is up to you.

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