Java InputMismatchException

问题

I have this code and I want to catch the letter exception but it keeps having these errors:

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)

And here is my code:

 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");

     }
 }

回答1:

You can use a do-while loop instead to eliminate the first 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);

Therefore all InputMismatchException can be handled in one place.

回答2:

from the doc

Scanner.nextInt Scans the next token of the input as an int. if the next token does not match the Integer regular expression, or is out of range

So it seems you are not entering any integer as input.

you can use

     while (students <= 0) {

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

            students = input1.nextInt();

         }

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

来源：https://stackoverflow.com/questions/16816250/java-inputmismatchexception

标签

java

exception-handling

while-loop

try-catch

mismatch