[antlr-interest] Java boolean type storage

[Andy Tripp]

Steve Lianoglou wrote:

> Hi guys,
>
> I've been casually following this thread and don't have much to say,  
> but I would like to point out:
>
>> That's a great example. You make the assumption that an array of  
>> booleans is somehow going to be slower or use more memory
>> than a bitvector. You've got to let that old thinking go, Luke! You  
>> worry about your application and pick the appropriate
>> data structure for it. Let the compiler and runtime be smart about  
>> performance and memory management. It is better at
>> those things than you are (and certainly better than you think it is).
>
>
> At some point an array of booleans (boolean[]) in Java actually used  
> one byte to store each bit, so appearances aren't always what they  
> seem? That's an 8x bigger data structure than you would have been  
> bargaining for ... and sometimes it really does make a difference.
>
> And by "at some point" .. this was seemingly the case in Java 1.2.2.

The place to look would be the JVM spec, which has only this footnote:
In Sun's JDK releases 1.0 and 1.1, and the Java 2 SDK, Standard Edition, 
v1.2, |boolean| arrays in the Java programming language are encoded as 
Java virtual machine |byte| arrays, using 8 bits per |boolean| element.

So that sounds like you're outta luck for now, but the spec doesn't rule 
out a change in the future.
Sorry, I didn't mean to get your hopes up :)

>
> (2) Maybe swerve the conversation to more tangible topics :-)

Not likely :) As with older languages, better to let older threads that 
have gone off track
just fade away quietly :)

>
> I should probably ask in comp.lang.java or some such, but how many  
> times does this thing come up in a passing conversation? I just  
> couldn't resist.
>
> Thanks,
> -steve
>