分别用while语句、do-while语句、for语句编写程序，计算e≈1+1/1!+1/2!+...+1/n!

使用while语句计算e≈1+1/1!+1/2!+...+1/n!的代码如下所示：

int n = 20;
double sum = 1.0, number = 1.0;
int i = 1;
while (i <= n) {
    number /= i;
    sum += number;
    i++;
}
System.out.println("使用while循环计算的e≈" + sum);

使用do-while语句计算e≈1+1/1!+1/2!+...+1/n!的代码如下所示：

int n = 20;
double sum = 1.0, number = 1.0;
int i = 1;
do {
    number /= i;
    sum += number;
    i++;
} while (i <= n);
System.out.println("使用do-while循环计算的e≈" + sum);

使用for语句计算e≈1+1/1!+1/2!+...+1/n!的代码如下所示：

int n = 20;
double sum = 1.0, number = 1.0;
for (int i = 1; i <= n; i++) {
    number /= i;
    sum += number;
}
System.out.println("使用for循环计算的e≈" + sum);