程序中的Java运行时错误InputMismatchException

Question

当我运行此代码时，我在coderunner（一个提交代码用于学校作业的应用程序）中获取此代码

    Scanner scan = new Scanner(System.in);

    double maxn = -90;
    double maxs = 90;
    double maxe = 180;
    double maxw = -180;
    double lat = 0;
    double longa = 0;
    int x = 1;

    while (x != 0) {
        System.out.println("Please enter a latitude:");
        lat = scan.nextDouble();
        if (lat >= maxn && lat <= 90)
            maxn = lat;
        if (lat <= maxs && lat >= -90)
            maxs = lat;

        System.out.println("Please enter a longitude:");
        longa = scan.nextDouble();
        if (longa <= maxe && longa >= -180)
            maxe = longa;
        if (longa >= maxw && longa <= 180)
            maxw = longa;

        System.out.println("Would you like to enter another location?");
        x = scan.nextInt();

    }
    System.out.println("Farthest North: " + maxn + "\nFarthest South: " + maxs + "\nFarthest East: " + maxe + "\nFarthest West: " + maxw);

我收到以下错误：

    Runtime Error

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:864)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at Lesson_20_Activity.main(Main.java:315)
at Ideone.assertRegex(Main.java:85)
at Ideone.assertRegex(Main.java:76)
at Ideone.test(Main.java:40)
at Ideone.main(Main.java:29)

我不知道这个错误是如何工作的，因为我不熟悉编码。有人可以解释这意味着什么以及如何解决它？

编辑：我的意见是

Please enter the latitude:
41.678
Please enter the longitude:
69.938
Would you like to enter another location?
1
Please enter the latitude:
41.755
Please enter the longitude:
69.862
Would you like to enter another location?
1
Please enter the latitude:
41.829
Please enter the longitude:
69.947
Would you like to enter another location?
1
Please enter the latitude:
300
Please enter the longitude:
69.947
Incorrect Latitude or Longitude
Please enter the latitude:
41.827
Please enter the longitude: 
69.904
Would you like to enter another location?
0
Farthest North: 41.829
Farthest South: 41.678
Farthest East: 69.947
Farthest West: 69.862

另外，我尝试将x更改为double和字符串输入，但没有成功。我得到的错误是NoSuchElementError和NoSuchLineError（分别）

Answer 1

从Javadoc，InputMismatchException投掷时：

由扫描程序抛出，表示检索到的令牌与预期类型的​​模式不匹配，或者令牌超出预期类型的​​范围。

在你的代码中，你正在调用scan.nextInt()和scan.nextDouble()。确保您只分别向这些调用中传递有效的int和double值。也就是说，当Scanner期望int值（scan.nextInt()）时输入double值会引发上述错误。

Answer 2

请注意，当您不想换行时，您应该使用System.out.print然后写'\ r \ n'。

我已经运行了您的代码并得到了正确的输出，但您必须注意您对命令行的输入。我读了所有字符串，然后转换为所需的原始格式，以避免此错误。

Answer 3

输入经度和纬度后，您要问的是再次尝试的问题。

x= nextInt()

在这里，你接受一个int（0来关闭while循环，否则）。如果在那里键入任何字符串或double值，将导致Inputmismtach异常。我尝试了你的代码，如果正确地给出了这些整数和小数，它可以正常工作，如下所示。

Please enter a latitude:
12.3
Please enter a longitude:
14.3
Would you like to enter another location?
1
Please enter a latitude:
12.3
Please enter a longitude:
14.5
Would you like to enter another location?
0
Farthest North: 12.3
Farthest South: 12.3
Farthest East: 14.3
Farthest West: 14.5