Java InputMismatchException

Question

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");

     }
 }    

Answer 1

You can use a do-while loop instead to eliminate the first input.nextInt().

int students = 0;
do {
    try {
        // Get input 
        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);

// Do something with guaranteed valid value 

Therefore all InputMismatchException can be handled in one place.

Answer 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();
         }
     }