String vs StringBuffer

The following article explains with simple examples when it is more efficient to use the + operator vs StringBuffer.append to concatenate Strings.  It explains that the choice depends on the nature of the strings.  Use + if they are all resolvable at compile time.  Use StringBuffer if they are only resolvable at run time.

http://www.precisejava.com/javaperf/j2se/StringAndStringBuffer.htm

Callable vs Runnable

Difference between Java's Callable and Runnable interfaces:
http://geekexplains.blogspot.com/2008/05/callable-interface-vs-runnable.html

Distributed Java EE Approach to Collatz Problem

I found this to be a very interesting article.  It tests the Collatz Problem through a distributed solution utilizing many Java EE related technologies.  It measures the performance of different combinations of hardware and software solutions.  Would like to recreate this on a my own distributed network.

http://mathworld.wolfram.com/CollatzProblem.html
http://wiki.eclipse.org/EclipseLink/Examples/Distributed

Expert Systems

Quickly read this article on wikipedia: http://en.wikipedia.org/wiki/Expert_system

I wonder if the UN or other well-funded organisations have tried to create an expert system to aid in decision making for conflict management, international development, and other big world issues.