JDK 8 RFR for JDK-8022658: Revisit FunctionalInterface on some core libs types

[Joe Darcy]

I was on the fence for Iterable too. Other opinions?

Thanks,

-Joe

On 10/21/2013 11:47 AM, Brian Goetz wrote:
> Of these, the only one I might question is Iterable.  While it is 
> commonly used as a mixin like Closeable or Flushable, unlike the 
> others, Iterables also make sense to stand on their own, and there are 
> some libraries that truck entirely in Iterable to perform stream-like 
> behavior (being the least-common-denominator "access to elements" 
> type.)  But, I can go either way on this.
>
> On 10/21/2013 2:16 PM, Joe Darcy wrote:
>> Hello,
>>
>> Earlier in JDK 8, various core library classes were annotated with the
>> @FunctionalInterface annotation (JDK-8005623 Retrofit
>> FunctionalInterface annotations to core platform interfaces). As
>> experience has been gained with the feature, the time has come to
>> revisit some of those annotations under issue
>>
>>      JDK-8022658: Revisit FunctionalInterface on some core libs types
>>
>> In brief, I propose removing @FunctionalInterface from the following six
>> types:
>>
>>   src/share/classes/java/io/Closeable.java
>>   src/share/classes/java/io/Flushable.java
>>   src/share/classes/java/lang/AutoCloseable.java
>>   src/share/classes/java/lang/Comparable.java
>>   src/share/classes/java/lang/Iterable.java
>>   src/share/classes/java/lang/Readable.java
>>
>> In these cases, the single method of the interface is more so a
>> mix-in/trait like feature and not readily usable standalone in a lambda
>> expression. Patch below.
>>
>> Thanks,
>>
>> -Joe
>>