how to handle a exception in java

Question

So I am using HtmlUnit, and the method's signature looks like:

public HtmlAnchor getAnchorByText(String text)
                           throws ElementNotFoundException

So this means, the call to this method won't just return null, but it will throw an exception.

(I find this a pain!!, in c# methods usually just return a null if not found, way easier unless I am missing something??)

So I HAVE to wrap this call in an exception if I don't want my application to crash right?

How do I do this in Java?

reference: http://htmlunit.sourceforge.net/apidocs/index.html

Don't forget that sometimes null is a valid return value so you can't always use it to signify a problem. Or there may be more than one thing that can go wrong so returning null isn't enough to tell you what the problem is. I guess I'm trying to say you'll be happier if you can understand how exceptions are meant to be used rather than seeing them as a hoop that must be jumped through. — David
– David, Commented Jan 6, 2010 at 4:01
Also note that just because it can be thrown (the "throws" clause just states the possibility of the exception being thrown) does not mean it will be. — matt b
– matt b, Commented Jan 6, 2010 at 4:05

cletus · Accepted Answer · 2010-01-06 03:33:59Z

6

Bear in mind that ElementNotFoundException is not a checked exception so you could ignore it. But if the element not being there is a valid case that you don't want an exception thrown in then yes you will have to wrap the code in a try-catch block and deal with it.

I too find this kind of flow-control-by-exceptions painful. The basic construct you want is:

HtmlAnchor anchor = null;
try {
  htmlAnchor = getAnchorByText(text);
} catch (ElementNotFoundException) {
  // do nothing
}

If you find yourself writing this sequence a lot then wrap it in a helper method:

public static HtmlAnchor myFindAnchor(String text) {
  try {
    return getAnchorByText(text);
  } catch (ElementNotFoundException) {
    return null;
  }
}

and call that instead of littering your code with spurious try-catch blocks.

answered Jan 6, 2010 at 3:33

cletus

627k169 gold badges922 silver badges945 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Noon Silk · Accepted Answer · 2010-01-06 03:33:56Z

1

-- Edit:

See cletus' answer; I assumed it was a checked exception because of the OPs description.

-- Old answer:

You just put a try/catch around it (or re-throw it from your method).

They are called "checked" exceptions, in Java, and are generally considered a mistake :) (but this is not really worth debating here).

try {
    getAnchorByText(,,,)
} catch (ElementNotFoundException enfe) {
    ///
}

or the throws:

public void myFoo (...) throws ElementNotFoundException

The idea is that you should not pass exceptions up to places that can't deal with them though (or at least, wrap it in something they can deal with). You try and constrain exceptions to varying 'levels' within your app.

answered Jan 6, 2010 at 3:33

Noon Silk

55.4k6 gold badges91 silver badges105 bronze badges

5 Comments

Noon Silk Over a year ago

Because only if it's checked do you need to handle it specifically, which is what he's complaining about.

Kaleb Brasee Over a year ago

I think there's some valid uses for checked exceptions, but yeah, they are generally overused.

Noon Silk Over a year ago

notnoop: Please see my revised edit. There is absolutely no point continuing this discussion.

notnoop Over a year ago

Thanks! Just noticed the change. Grr... I would love to give your your 2 points back ;-).

Noon Silk Over a year ago

No worries :) Probably I should actually check the links before I answer, sorry if I seemed rude :)

Collectives™ on Stack Overflow

how to handle a exception in java

2 Answers 2

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related