Java InputMismatchException

Question

我有这段代码，我想捕获字母异常，但它总是出现以下错误：

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:840)
    at java.util.Scanner.next(Scanner.java:1461)
    at java.util.Scanner.nextInt(Scanner.java:2091)
    at java.util.Scanner.nextInt(Scanner.java:2050)
    at exercise_one.Exercise.main(Exercise.java:17)

下面是我的代码：

 System.out.print("Enter the number of students: ");

 students = input.nextInt(); 

 while (students <= 0) {

     try {

        System.out.print("Enter the number of students: ");

        students = input.nextInt();

     }

     catch (InputMismatchException e) {

        System.out.print("Enter the number of students");

     }
 }    

Answer 1

您可以使用do-while循环来消除第一个input.nextInt()。

do {
    try {
        System.out.print("Enter the number of students: ");
        students = input.nextInt();
    } catch (InputMismatchException e) {
        System.out.print("Invalid number of students. ");
    }
    input.nextLine(); // clears the buffer
} while (students <= 0);

Answer 2

从doc

Scanner.nextInt将输入的下一个标记扫描为整数。如果下一个标记与整数正则表达式不匹配或超出范围

因此，您似乎没有输入任何整数作为输入。

您可以使用

     while (students <= 0) {

         try {
            System.out.print("Enter the number of students: ");

            students = input1.nextInt();

         }

         catch (InputMismatchException e) {
             input1.nextLine();
         }
     } 

Answer 3

从扫描仪读取数据并将其分配给Int类型。由于您提供的是字符串，这将抛出异常。要处理这种情况，必须只在Try- Catch块中编写代码片段。