Validating Command Line Arguments User Input

Question

It's been some years since I've used Java, and I'm not quite sure what the best practice for validating command line input is.

My code is currently structured like so:

while (true) {
    try { ... break; } catch(...) {...}
}

I feel that this is poor practice, because it's similar to using a goto statement in a way.

Is there a better way to validate user input?

Is simply using a boolean the preferred method?

Edit:

More specifically, validating user-input from the stdin (scanner).

Something to the extent of:

while(true){
    try {
        userInput = Integer.parseInt(stdin.next());
        break;
    } catch (InputMismatchException e) {
        ...
    }
}

Can you be more specific? What kind of validation are you talking about? While in while loop? — Crazyjavahacking
– Crazyjavahacking, Commented Jan 27, 2015 at 19:12
You may chechk this document: cse.yorku.ca/~mack/1011/InputValidation.PDF — pcejrowski
– pcejrowski, Commented Jan 27, 2015 at 19:20
That is an odd dup to mark this as. If anything I would have marked it as a dup of stackoverflow.com/questions/6456219/… but in reality it is slightly different than both of those questions. — chancea
– chancea, Commented Jan 27, 2015 at 19:30
For the record, I voted to close as primarily opinion-based, not as a dupe. — yshavit
– yshavit, Commented Jan 27, 2015 at 19:49

mbomb007 · Accepted Answer · 2015-01-28 16:07:54Z

1

Though what you have is acceptable, I prefer to at least output a message if what they entered doesn't match your validation.

Something more like this:

int userInput;
System.out.println("Please enter an integer:");
while(true){
    try {
        userInput = Integer.parseInt(stdin.next());
        break;
    } catch (InputMismatchException e) {
        System.out.println("Please enter a valid integer:");
    }
}

edited Jan 28, 2015 at 16:07

answered Jan 27, 2015 at 19:24

mbomb007

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1 Comment

yshavit Over a year ago

I would use the break rather than the valid flag, as the OP had originally. It has the same end effect, while being a bit simpler (why keep and update state you don't need?).

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