使用while循环返回整数的第一位和最后一位

Question

我一直在尝试编写一个使用while循环返回输入的第一个和最后一个数字的程序。

到目前为止我得到的是：

import java.util.Scanner;
public class FirstLastInt {
public static void main(String[]args)
{
    int fdig, ldig, num;

    Scanner in = new Scanner(System.in);

    System.out.println("Enter an Integer.");
    num = in.nextInt();

    ldig = num%10;

    while (num > 0)
    { fdig = num/10;
        num = num/10;

         System.out.println("The first digit is " + fdig + ", and the last digit is " + ldig + ".");
    }
}

run:
Enter an Integer.
98884
The first digit is 9888, and the last digit is 4.
The first digit is 988, and the last digit is 4.
The first digit is 98, and the last digit is 4.
The first digit is 9, and the last digit is 4.
The first digit is 0, and the last digit is 4.
BUILD SUCCESSFUL (total time: 3 seconds)

看起来循环在我得到我想要的数字之前和之后运行。有没有指定哪一行我想打印？（在示例中，它是“第一个数字是9，最后一个数字是4。”）

Answer 1

如果您希望继续使用自己的代码来查看如何通过这种方式实现，那么更改while条件并将系统打印移到外部：

import java.util.Scanner;
public class FirstLastInt {
    public static void main (String[] args) {
        int ldig, num;

        Scanner in = new Scanner(System.in);

        System.out.println("Enter an Integer.");
        num = in.nextInt();

        ldig = num % 10;

        // keep looping num until it is in the range of 0-9
        while (num >= 10) {
            num = num / 10;
        }
        //initialize fdig variable and set it equal to num, just to make things clearer
        int fdig = num;

        System.out.println("The first digit is " + fdig + ", and the last digit is " + ldig + ".");
    }
}