Question on Primitive Types in Patterns

[Brian Goetz]

>
> I've been giving a presentation on Patterns in the Java language and 
> including some puzzles.  The recent inclusion of Primitive Types in 
> Patterns has provided some interesting material.  I currently have one 
> puzzle that I can't quite explain; hopefully someone on the mailing 
> list can provide clarification.

On a pedagogical note, I'd like to make a case for "Java Puzzlers Talks 
Considered Harmful."  They can be fun to write (which is why we get so 
many of them), but I have found that the vast majority of time, a good 
chunk of the audience comes away with notions that are closer to "XYZ is 
broken", "XYZ is just all ad-hoc complexity", or "XYZ has no organizing 
design principle" -- even though this is rarely the intent of the 
presenter (often the opposite, in fact.)

When Josh and Neal started with Puzzlers, they could at least come from 
the position of "these were some arguably-mistakes that *we* made".  Not 
only did this give them credibility that almost no other "Java Puzzlers" 
presenter could have, but it pushed them to dig deeper to present 
language design tradeoffs _from the perspective of language designers_.

I cannot count the number of times where someone has seen a "puzzler" 
presentation or blog, and learned the exact opposite lesson than it was 
trying to teach.   This is an extraordinarily difficult format for 
teaching.  Worse, the nature of a "Puzzlers" talk requires having a 
bunch of them, and -- even when Josh and Neal did it -- there were 
always a few that didn't live up to the standards; the format often 
overtakes the message.  It is just a truly punishing format, one that 
requires world-class pedagogy and impeccable preparation to avoid the 
all-too-common outcome where many in the audience learn the wrong lesson 
(often reinforcing their preconceived but ill-examined assumptions about 
"X is bad.")