[OpenJDK 2D-Dev] <AWT Dev> What to override and what now

Artem Ananiev artem.ananiev at oracle.com
Wed Oct 26 15:27:35 UTC 2011

On 10/15/2011 12:30 AM, Mario Torre wrote:
> While working a bit on cacio, we just found some new nice addition to the Toolkit code, like this one:
>      public boolean areExtraMouseButtonsEnabled() throws HeadlessException {
>          GraphicsEnvironment.checkHeadless();
>          return Toolkit.getDefaultToolkit().areExtraMouseButtonsEnabled();
>      }
> Of course, this method is meant to be overridden, so it will end up doing nothing, but things like this may be very difficult to debug at times, and in any case, is definitely are not friendly code. Is there any reason for this smartness?

I completely agree. This code seems to be never called, otherwise it 
would fail into an infinite recursion, it shouldn't be any problems with 
it returning "false".

> Why not simply provide a default implementation or just throw an exception or simply make the method abstract? Or maybe I'm missing something?

Making it abstract is not a good idea: I know some rare cases when the 
Toolkit class is extended (e.g. for testing purposes), and adding a new 
abstract method will break such code at compile time.

> I hope there are not many more of those examples scattered around, or to know what to subclass and override will be a pain.



> Cheers,
> Mario
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