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Thread: InputMismatchException try catch block not working as expected

  1. #1
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    Cool InputMismatchException try catch block not working as expected

    Hi people, I'm new here!

    I have decided to write a small program to learn myself Java. i have created a function that should catch a mismatch exception and respond by asking for the data to be entered again. However, it does not work when I enter purposefully erroneous data.

    When I enter a String (should be an int) the loop goes round constantly. Not sure if its na infinate loop but i always end up resetting the Java Virtual Machine.

    The code:

    public int doPubYear()
        {
            boolean done = false;
            int pubYear = 0;
            while(!done){
                try{
                    System.out.print("Year of publication: ");
                    pubYear = keyboard.nextInt();
                    done = true;
                } catch(InputMismatchException e){
                    System.out.println("Error with input - try again.");
                }            
            }
     
            return pubYear;
        }

    I have :-
    import java.util.Scanner;
    import java.util.InputMismatchException;
    at the top.

    Thanks


  2. #2
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    Default Re: InputMismatchException try catch block not working as expected

    I have fixed it I needed to use keyboard.nextLine() to discard the input that the user previousley entered.

    My new code:

    public int doPubYear()
        {
            boolean done = false;
            int pubYear = 0;
            while(!done){
                try{
                    System.out.print("Year of publication: ");
                    pubYear = keyboard.nextInt();
                    done = true;
                } catch(InputMismatchException e){
                    System.out.println("Error with input - try again.");
                    keyboard.nextLine();
                }            
            }
     
            return pu

  3. #3
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: InputMismatchException try catch block not working as expected

    Hi Mikhl,

    Yea you found the solution indeed, it should be noted that nextInt() is in fact an interesting function in regards to the fact it does't disregard end line characters etc, which is what causes this seemngly odd behaviour.

    Glad you worked it out

    Chris
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

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