Event Handlers with Method References / Lambdas

Brian Goetz brian.goetz at oracle.com
Sun Apr 1 07:23:40 PDT 2012

> with some EventDispatcherImpl implementation that e.g. holds a
> List<EventDispatcher>  and dispatches to each in turn. Of course, for
> the reasons discussed in the lambda equality thread, in a real
> implementation we'd want to return a handle object from
> addEventHandler() so we can remove event handlers again later - but
> let's not worry about that for now.

Or just save the handler object you pass in.  (This is not a new 
problem; we have exactly the same problem when using anonymous classes 
for listeners.)

> Then I take it that this::onTemperatureChange is exactly equivalent to
> the lambda: (e) ->  { onTemperatureChange(e);}

Correct.  Method references can be thought of as shorthands for 
corresponding lambdas:

   Foo::staticMethod  ==>       (args) -> staticMethod(args)
   Foo::instanceMethod ==>      (arg0, rest) -> arg0.instanceMethod(rest)
   expr::instanceMethod ==>     (args) -> expr.instanceMethod(args)

> My question is, I'm using Henri Gomez's most recent Lambda build for
> OS X. I'm getting fairly regular (but not every time) crashes when
> running javadoc over TemperatureHandler (and occasional javac crashes
> as well) - is there a group that would be interested in the crash
> reports, or are we still expecting javac / javadoc to be
> inconsistently stable?

Yes!  Post it here.

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