Request for review: proposal for @FunctionalInterface checking

[Ali Ebrahimi]

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
>>
>
>