Default method survey results

[Paul Benedict]

Sorry, typo in last paragraph...
Forcing an implementation might just be going too far to evolve an interface.

On Thu, Aug 16, 2012 at 12:40 PM, Paul Benedict <pbenedict at apache.org> wrote:
> On Thu, Aug 16, 2012 at 12:32 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
>>
>>> Why not get rid of default implementations all together? Allow
>>> interfaces to be extended at will and the JVM simply throws a
>>> NotImplementedException (ala C# or Apache Commons Lang) if there is no
>>> overriding implementation.
>>
>>
>> Pushing the problem to runtime is not a good solution; a program that
>> compiles should not throw linkage errors.
>>
>
> I am not saying make this a linkage error -- something that would
> prevent the class from loading. Make this a runtime exception when you
> call a method that has no implementation. I think this is perfectly
> reasonable; the analogy is close to throwing
> UnsupportedOperationException when a developer doesn't really support
> the feature. The JVM can stub this "default implementation" of
> throwing an exception.
>
> This won't effect the compiler -- you still have to provide concrete
> implementations for all abstract methods when compiling a new. But if
> there's an existing library out there that's lagging behind, stub in
> the thrown exception.
>
> Now you can allow interfaces to evolve without or without a default
> implementation. Forcing an implementation might just be going to
> evolve an interface.
>
> Paul