如何读取可能是int或double的输入? [英] How do I read input that could be an int or a double?
问题描述
我正在编写一个程序,我需要从键盘输入。我需要输入一个数字,但我不确定它是 int
还是 double
。这是我的代码(针对该特定部分):
I'm writing a program in which I need to take input from the keyboard. I need to take a number in, yet I'm not sure if it's an int
or a double
. Here's the code that I have (for that specific part):
import java.io.*;
import java.util.*;
//...
Scanner input = new Scanner(System.in);
int choice = input.nextInt();
我知道我可以获得 String
和做 parseInt()
或 parseDouble()
,但我不知道它会是哪一个。
I know I can get a String
and do parseInt()
or parseDouble()
, but I don't know which one it'll be.
推荐答案
只要使用 double
,无论它是什么。使用双精度值时,没有明显的损失。
Just use a double
no matter what it is. There is no noticeable loss on using a double for integral values.
Scanner input = new Scanner(System.in);
double choice = input.nextDouble();
然后,如果你需要知道你是否已经获得双倍,你可以检查它使用 Math.floor
:
Then, if you need to know whether you've gotten a double or not, you can check it using Math.floor
:
if (choice == Math.floor(choice)) {
int choiceInt = (int) choice);
// treat it as an int
}
不要乱用 catch
ing NumberFormatException
,不要搜索字符串一段时间(这可能甚至不正确,例如,如果输入是 1e-3
它是一个双倍的( 0.001
),但没有句号。只需将其解析为 double
并继续前进。
Don't mess with catch
ing NumberFormatException
, don't search the string for a period (which might not even be correct, for example if the input is 1e-3
it's a double (0.001
) but doesn't have a period. Just parse it as a double
and move on.
此外,不要忘记两个 nextInt()
和 nextDouble()
不捕获换行符,所以你需要使用后用 nextLine()
捕获它。
Also, don't forget that both nextInt()
and nextDouble()
do not capture the newline, so you need to capture it with a nextLine()
after using them.
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