Request for review: proposal for @FunctionalInterface checking

[Ali Ebrahimi]

Thanks joe.

Ali

On Wed, Jan 9, 2013 at 2:39 AM, Joe Darcy <joe.darcy at oracle.com> wrote:

>  Hello Ali,
>
> Use of @FunctionalInterface is optional and is just done to allow stricter
> compile-time checking.  If a functional interface is *not* annotated with
> @FunctionalInterface, it can still be used for lambda expressions, etc.
>
> Cheers,
>
> -Joe
>
>
> On 01/08/2013 02:07 PM, Ali Ebrahimi wrote:
>
> Hi joe,
>
> does this mean if functional interfaces do not be annotated with
> @FunctionalInterface annotation can not be used in lambda expressions.
>
> general question: annotating of functional interfaces is required or
> optional?
> I ask this for this purpose that there is huge number of functional
> interfaces in java legacy third parties code base that all are candidate
> for use in lambda expressions and can not be retrofired to annotated with
> this annotation.
>
> Ali
>
> On Wed, Jan 9, 2013 at 12:34 AM, Joe Darcy <joe.darcy at oracle.com> wrote:
>
>> Hello,
>>
>> While there were some reservations expressed about this proposal, there
>> were no strong objections so I'm going forward with adding this annotation
>> type to the platform, with a somewhat refined specification.
>>
>> Thanks,
>>
>> -Joe
>>
>>
>> On 12/28/2012 1:38 PM, Joe Darcy wrote:
>>
>>> Hi Sam,
>>>
>>> On 12/28/2012 12:28 PM, Sam Pullara wrote:
>>>
>>>> On Dec 28, 2012, at 3:02 PM, Joe Darcy <joe.darcy at oracle.com <mailto:
>>>> joe.darcy at oracle.com>> wrote:
>>>>
>>>>> has exactly one abstract method.  Since default methods are not
>>>>> abstract, any default methods declared in an interface do not contribute to
>>>>> its abstract method count.  If an interface declares a method overriding
>>>>> one of the public methods of java.lang.Object, that also does <em>not</em>
>>>>> count toward the abstract method count.
>>>>>
>>>>
>>>> This is pretty murky. This works:
>>>>
>>>> interface Foo {
>>>>   @Override
>>>>   boolean equals(Object other);
>>>> }
>>>>
>>>> but if you try this
>>>>
>>>> interface Foo {
>>>>   @Override
>>>>   default boolean equals(Object other) {
>>>>     return false;
>>>>   }
>>>> }
>>>>
>>>> it does give an error that says I can't override:
>>>>
>>>> *java: default method equals in interface spullara.Foo overrides a
>>>> member of java.lang.Object*
>>>>
>>>> Seems like "override" is the wrong word to use and will likely be
>>>> confusing since we are explicitly disallowing the second one.
>>>>
>>>>
>>>>
>>> Yes, I was contemplating whether "override" was the best phrasing to use
>>> in the wording above because of this sort of wrinkle. Instead "*abstract*
>>> method overriding one of the ..." might help distinguish this particular
>>> case.
>>>
>>> -Joe
>>>
>>
>>
>
>