java中用while循环计算1+1/2!+1/3!+...+1/20!之和

public class Example_02 { public static void main(String args[]) { double sum = 0,a = 1; int i = 1; while(i <= 20) { sum = sum+a; i = i+1; a = a*(1.0/i); } System.out.println(sum); } }