Support for adding multiple handlers for the same event in Java Robots API

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In the Python Robots API, there method robot.Robot.register_handler states 
(correctly, I believe) that "Multiple handlers may be registered on a single 
event type and are guaranteed to be called in order of registration." However, 
in the Java Robots API, the only way I can find to define event handlers is to 
override the appropriate method of AbstractRobot -- so I may only define one 
event handler for any given event. 

I would like some way to define multiple handlers for the same event in the 
Java API, just as I can with register_handler in the Python API.

I realise that I could "multiplex" two event handlers into one just by running 
one after the other, allowing me to do this. However, I cannot be so precise 
about contexts and filters this way as I could in the Python API. For instance, 
consider the following code in the Python API:

bot.register_handler(events.DocumentChanged, handler1, context=[ALL], 
filter="specific_filter")
bot.register_handler(events.DocumentChanged, handler2, context=[SELF], 
filter="general_filter")

I expect handler2 to be triggered much more often than handler1 (because the 
filter is somehow more general), but that's okay because it requires in a 
smaller context. If I were to try translating this into the Java API by just 
running the two handlers one after another, I would be forced to set the 
context to ALL, and to use the more general filter -- so now the handler is 
triggered frequently, with the whole context.

Original issue reported on code.google.com by reiner.p...@gmail.com on 28 Dec 2010 at 9:30