Exception handling with a do-while loop in Java

Question

The algorithm should take in 3 integers to an ArrayList. If the input is not an integer, then there should be a prompt. When I execute my code the catch clause is e

Answer 1

That is because when the next int is read using nextInt() and it fails, the Scanner still contains the typed contents. Then, when re-entering the do-while loop, input.nextInt() tries to parse it again with the same contents.

You need to 'flush' the Scanner contents with nextLine():

catch (Exception exc) {
    input.nextLine();
    System.out.println("invalid number");
}

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Notes:

• You can remove the counter variable, because you're not using it. Otherwise, you could replace counter += 1 by counter++.
• You can replace while (!(numbers.size() == 3)) with while (numbers.size() != 3), or even better: while (numbers.size() < 3).
• When catching exceptions, you should be as specific as possible, unless you have a very good reason to do otherwise. Exception should be replaced by InputMismatchException in your case.