Java第三课:1!+1/2!+1/3!+1/4!+....的前20项和

FOR循环计算

public class factorial2{    public static void main(String arg[]){    double a,b=1,c=0;    System.out.println("1!+1/2!+1/3!+1/4!+....的前20项和：");        for(a=1;a<=20;a++){            b*=1/a;             //求1/n!            c+=b;               //20个1/n!之和        }        System.out.println(c);          //输出结果    }}

do-while循环计算

public class factorial3{    public static void main(String arg[]){        double a=1,b=1,c=0;        System.out.println("1!+1/2!+1/3!+1/4!+....的前20项和:");        do{            b*=(1/a);       //求1/n!            c+=b;           //20个1/n!之和            a++;                    }while(a<21);           //判断循环        System.out.println(c);      //输出结果    }}