poj 1517 u Calculate e(精度控制+水题)

一、Description

A simple mathematical formula for e is

e=Σ0<=i<=n1/i!

where n is allowed to go to infinity. This can actually yield very accurate approximations of e using relatively small values of n.
Input

No input
Output

Output the approximations of e generated by the above formula for the values of n from 0 to 9. The beginning of your output should appear similar to that shown below.

二、题解

注意精度的控制，结果控制在9位小数，String .format("%.9f",sum)。

三、java代码

public class Main {

public static void main(String[] args) {
int i,j,fac;
double sum=2.5d;
System.out.println("n "+"e");
System.out.println("- "+"-----------");
System.out.println("0 "+"1");
System.out.println("1 "+"2");
System.out.println("2 "+"2.5");
for(i=3;i<10;i++){
fac=1;
for(j=1;j<=i;j++){
fac*=j;
}
sum+=1.0 /(fac);
System.out.print(i+" ");
System.out.println(String .format("%.9f",sum));
}
}
}