Tuesday, September 20, 2011

IBM Java 7 is now available

IBM Java 7 was officially released yesterday, September 19. You can download it from IBM DeveloperWorks.

There are a lot of exciting new features including a number of GC improvements.

  • The balanced GC policy, which I've mentioned before, is included in all 64-bit Java 7 JDKs. You can enable it with -Xgcpolicy:balanced.
  • The soft-realtime garbage collector is included for evaluation on Linux and AIX. It can be enabled with -Xgcpolicy:metronome.
  • The verbose GC format has been completely overhauled. It now provides more information and the XML format has been redesigned to make machine interpretation of the data simpler, allowing both IBM and customers to write tools to process and analyse the data.

Friday, September 2, 2011

"Don't do what Donny Don't does"

Thank to Evan Hughes for pointing out this paper: Conditional statements, looping constructs, and program comprehension: an experimental study.

Not surprisingly, negative conditions are more difficult to understand than positive conditions.

I always try to write conditions to be positive. Sometimes, I'll even include an empty 'if' block so that I can put code in the 'else' block instead of using a negative condition:

   if (isInRange(value)) {
      // expected case; do nothing
   } else {
      throw new OutOfRangeException(value);

I haven't read the full paper, so maybe the researchers answered my next question: is the problem exacerbated by the syntax for negative conditions used in C-like languages? I find that the '!' operator uses very little horizontal space, making it less noticeable than other unary operators such as '~' or '*'.

e.g. would this statement:

   if (!isInRange(value)) { ...

be more obvious if it were written like this?

   if (not isInRange(value)) { ...