Java的for循环 、do-while、while三种方法求n的阶乘_java用for循环实现5的阶乘

for循环：

package com.study;
import java.util.Scanner;
public class CountFor {
    public static void main(String[] args) {
        int x;
        int sum=1;
        System.out.println("请输入数字n：");
        Scanner  in=new Scanner(System.in);
        int i=in.nextInt();
        String s = " ! =";
        for(x=1;x<=i;x++){
            sum=sum*x;
            if (x<i){
                s = s + x+ '*' ;
            }
            else{
                s = s  + x + "=" + sum;
            }
        }
        System.out.println(i+s);
    }
}

do-while：

package com.study;
import java.util.Scanner;
public class CountDo {
    public static void main(String[] args) {
        int x=1;
        int sum=1;
        System.out.println("请输入数字n：");
        Scanner in=new Scanner(System.in);
        int i=in.nextInt();
        String s = " ! =";
        do {
            sum=sum*x;
            if (x<i){
                s = s + '*' + x;
            }
            else{
                s = s +"*" + x + "=" + sum;
            }
            x++;
        }while(x<=i);
        System.out.println(i+s);
    }
}

while：

package com.study;
import java.util.Scanner;
public class CountWhile {
    public static void main(String[] args) {
        int x=1;
        int sum=1;
        System.out.println("请输入数字n：");
        Scanner in=new Scanner(System.in);
        int i=in.nextInt();
        String s = " ! =";
        while(x<=i){
            sum=sum*x;
            if (x<i){
                s = s + '*' + x;
            }
            else{
                s = s +"*" + x + "=" + sum;
            }
            x++;
        }
        System.out.println(i+s);
    }
}