Loose ends: Optional

Remi Forax forax at univ-mlv.fr
Tue May 28 09:10:26 PDT 2013

On lambda-dev: 05/28/2013 05:35 PM, brian.goetz at oracle.com wrote:
> Changeset: fde3666e6394
> Author:    briangoetz
> Date:      2013-05-28 11:34 -0400
> URL:http://hg.openjdk.java.net/lambda/lambda/jdk/rev/fde3666e6394
> Additional convenience methods on Optional
> ! src/share/classes/java/util/Optional.java

It seems, I have not received one or several emails about adding an 
eager versions of filter, map to Optional.
The last email I received about that subject is the one below.


On 05/25/2013 07:12 PM, Remi Forax wrote:
> On 05/24/2013 10:15 PM, Brian Goetz wrote:
>> Optional has obvious upsides and downsides.  Some of the downsides are:
>>  - It's a box.  Boxing can be heavy.
>>  - The more general-purpose value-wrapper classes you have, the more 
>> some people fear an explosion of unreadable types like 
>> Map<Optional<List<String>>, List<Optional<Map<String, 
>> List<Optional<String>>> in API signatures.
>> I think where we've tried to land is: do things that encourage people 
>> to use Optional only in return position.  These methods make it more 
>> useful in return position while not increasing the temptation to use 
>> it elsewhere any more than we already have. Hence "mostly harmless".
> I think you cross a line without seen it, filter, map and flatmap are 
> lazy on Stream but not on Optional.
> Rémi
>> On 5/24/2013 4:10 PM, Tim Peierls wrote:
>>> On Fri, May 24, 2013 at 3:20 PM, Brian Goetz <brian.goetz at oracle.com
>>> <mailto:brian.goetz at oracle.com>> wrote:
>>>     Proposed spec for methods on Optional, which would have the obvious
>>>     counterparts in Optional{Int,Long,Double}.
>>>     These methods are known to be useful and seem mostly harmless now
>>>     that other things have settled.  (I don't think they greatly
>>>     increase the moral hazard of Optional in general, and they do make
>>>     it more expressive.)
>>> I'm in the curious (unique?) position of both desperately wanting
>>> Optional and desperately *not* wanting lots of additional methods like
>>> these. If the price of having Optional is the presence of these 
>>> methods,
>>> I'll suck it up, but "mostly harmless" is not exactly a ringing 
>>> endorsement.
>>> --tim

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