hg: lambda/lambda/jdk: Cleanup in Optional

[Roland Tepp]

I wonder, why use Optional, if you already know, if the value is either
null on non-null?

I'd use Optional only in the case I have a reasonable expectation that the
value might be missing, but I still want to provide a fairly linear
processing of this case.

I can see no use case for using null checks and Optional side-by-side -
either use one or the other.

2012/11/23 Ricky Clarkson <ricky.clarkson at gmail.com>

> Actually I can think of plenty of times when that is exactly what I wanted.
> On Nov 23, 2012 9:09 AM, "Gernot Neppert" <mcnepp02 at googlemail.com> wrote:
>
> > I don't think it's realistic to be "thinking you do not have null and
> > you'd rather have an exception".
> > Either I know the value is null, then I may call empty(), or I don't
> know,
> > in which case I wouldn't want to invoke a method that might throw an
> > Exception. I'd rather get a valid 'Optional' instance, be it empty or
> not.
> >
> > Note that everything would be different if 'Optional' were allowed to
> have
> > 'null' values. Then of course we'd need to be able to discriminate
> between
> > 'No value at all' and 'The value null'. But since that has been voted
> down,
> > the reason for having distinct factory methods has (IMO) gone away.
> >
> >
> > > You might be calling .of(T) thinking you do not have null and you'd
> > rather have an exception than an empty Optional as the result.
> >
> >
> > 2012/11/23 Ricky Clarkson <ricky.clarkson at gmail.com>
> >
> >> That's a useful method but I'd suggest calling it 'option' or
> >> 'fromNullable'.  You might be calling .of(T) thinking you do not have
> null
> >> and you'd rather have an exception than an empty Optional as the result.
> >>  For reference, Scala calls it option, Guava calls it fromNullable,
> >> Functional Java calls it fromNull and all 3 make that a distinct method
> >> from the one that throws an exception if it's null (Some(t) in Scala,
> of in
> >> Guava, some(t) in Functional Java).
> >>
> >>
> >> On Fri, Nov 23, 2012 at 5:36 AM, Gernot Neppert <
> mcnepp02 at googlemail.com>wrote:
> >>
> >>> Hi Brian,
> >>>
> >>> I do think that having factory methods 'empy()' and 'of(T)' and no
> public
> >>> constructor is a good thing, I wonder whether it's necessary to make
> >>> 'of(T)' is so restrictive: it throws NullPointerException if the
> supplied
> >>> value is null.
> >>> So why place the burdon of picking the correct factory method upon the
> >>> user?
> >>> Why not simply have:
> >>>
> >>> public static <T> Optional<T> of(T value) {
> >>>   return value == null ? empty() : new Optional<T>(value);
> >>> }
> >>>
> >>>
> >>>
> >>>
> >>> 2012/11/15 <brian.goetz at oracle.com>
> >>>
> >>> > Changeset: ab258565c0c9
> >>> > Author:    briangoetz
> >>> > Date:      2012-11-15 17:19 -0500
> >>> > URL:
> >>> http://hg.openjdk.java.net/lambda/lambda/jdk/rev/ab258565c0c9
> >>> >
> >>> > Cleanup in Optional
> >>> >
> >>> > ! src/share/classes/java/util/Optional.java
> >>> > ! src/share/classes/java/util/streams/ops/FindAnyOp.java
> >>> > ! src/share/classes/java/util/streams/ops/FindFirstOp.java
> >>> > ! src/share/classes/java/util/streams/ops/SeedlessFoldOp.java
> >>> >
> >>> >
> >>> >
> >>>
> >>>
> >>
> >
>
>


-- 
Roland