阶乘 Java 程序

Question

我想用 for 循环在 java 中做一个阶乘程序。例如，我想获取用户输入，比如说10，然后乘以10*9*8*7*6*5*4*3*2*1。我需要帮助构建for 循环。到目前为止，我不知道该去哪里，所以下面的代码就是我所拥有的。

import java.util.Scanner;
import java.lang.Math;
public class factorial {

    public static void main(String[] args) {
        int num;
        Scanner input = new Scanner(System.in);
        System.out.println("Enter a number: ");
        num = input.nextInt();
    }
}

Answer 1

递归函数编码：

import java.util.Scanner;

public class Main {

     public static void main(String[] args)
     {
         System.out.print("Enter a number: ");
         Scanner input = new Scanner(System.in);
         int num = input.nextInt();
         long factorialResult = factorialRecursive(num);
         System.out.println(factorialResult);
     }


     public static long factorialRecursive(int n) {
         if (n == 0 || n == 1 )
             return 1;

         return n * factorialRecursive(n - 1);
     }
}

来源：learn.uncox.com

如果数字很大，就会发生“stackoverflow”。

Answer 2

试试

public static void main(String[] args) {
    int num;
    int fact=1;
    Scanner input = new Scanner(System.in);
    System.out.println("Enter a number: ");
    num = input.nextInt();
    for (int i=2;i<=num; i++){
        fact=fact*i;
    }

    System.out.println("Factorial: "+fact);
}

正如@Marko Topolnik 在 cmets 中提到的，此代码适用于最多 12 个输入。对于较大的输入，由于溢出，将输出无穷大。

对于大于 12 的数字，您应该使用更高的数据类型，例如 BigInteger

你可以试试：

public static void main(String[] args) {
    BigInteger num;
    BigInteger fact = BigInteger.valueOf(1);
    Scanner input = new Scanner(System.in);
    System.out.println("Enter a number: ");
    num = input.nextBigInteger();
    for (int i = 2; i <= num; i++){
        fact = fact.multiply(BigInteger.valueOf(i));
    }
    System.out.println(fact);
}

Answer 3

何必计算呢？

public int factorial ( int n ) {
switch(n){
case 0: return 1;
case 1: return 1;
case 2: return 2;
case 3: return 6;
case 4: return 24;
case 5: return 120;
case 6: return 720;
case 7: return 5040;
case 8: return 40320;
case 9: return 362880;
case 10: return 3628800;
case 11: return 39916800;
case 12: return 479001600;
default : throw new IllegalArgumentException();
}

来源：@Emory

Answer 4

这是我的节目

class FactorialUsingFor
{
    public static void main(String arg[])
    {
        int factorial = 1;
        int number = 6;

        for(int i = 1; i <= number; i++)
        {
            factorial *= i;
        }

        System.out.println("Factorial of number " + number + " is " + factorial);

    }
}

Answer 5

int sum = 1;

for (int i = 2;i <= num;i++) {
    sum = sum * i;
}

Answer 6

试试这个程序：=

import java.util.*;
public class Factorials {
 public static void main(String[] args){
  Scanner sc=new Scanner(System.in);
  int i,num,a,b;
  int c=1;
  System.out.println("Enter the no.= ");
  num=sc.nextInt();
  for(i=1;i<=num;i++){
   c=i*c;
  }
  System.out.println("Factorial is "+c);
 }
}

Answer 7

import java.util.Scanner;
public class Factorial {
    public static void main(String[] args){
        Scanner scn = new Scanner(System.in);
        System.out.println("Enter the number to find factorial");
        int o=scn.nextInt();
        int count=0,b=o-1,res=(o*(o-1)),r=0;
        while(count!=1)
        {
         count=b-1;
         r=count*res;
         res=r;
         r=1;
         b=b-1;
        }
        System.out.println(res);
    }
}