Optional require(s) NonNull

[Roland Tepp]

2012/10/30 Alessio Stalla <alessiostalla at gmail.com>

> On Tue, Oct 30, 2012 at 4:02 PM, Roland Tepp <luolong at gmail.com> wrote:
> > 2012/10/30 Brian Goetz <brian.goetz at oracle.com>
> > The danger of having a get() method directly on Optional is that this
> > encourages the direct use of optional.get() which is susceptible to
> > NoSuchElementException with the same casualty as NullPointerException's
> are
> > common without use of Optional.
>
> There is a big difference: with get(), the exception occurs at the
> exact location where you call get(), i.e. as soon as you need to pass
> your Optional value to some method that expects non-optional values.
> The problem with NPEs is not that they are thrown, but that they can
> be thrown far away from the code that actually caused them.


>

No, not really.

NPE happens whenever you are trying to use (actually dereference) an object
that is null.
Same is with optional. You get the NSEE when you try to use the value that
is not there.
It might be slightly earlier than with nullable objects, but effectively
the result is same.


> > Moving it out of the Optional and into the Some/Present will require
> > explicit casting of the Optional to Present which at least is more
> > deliberate action and force the developer to consider this at least for a
> > moment.
> > i.e. something like this:
> >     Optional<String> optional = ...
> >     if (optional.isPresent()) {
> >         ((Present) optional).get().split(...);
> >     }
>
> If you already bothered to guard it with if (optional.isPresent()) why
> the need for casting? And, if you don't guard it, it will fail with a
> CCE just as if it would have failed with a NoSuchElementException.
>

Because casting an object is considered dangerous operation without
guarding the cast.
That is exactly it - it forces me into thinking about weather the cast is
safe as opposed exposing a potentially dangerous (as in - it may blow up in
your face) to user without predudice.

-- 
Roland