When running Drools unit tests on Solaris with Sun JDK 6, the following test throws a SOE:

org.drools.jsr94.rules.StatefulRuleSessionTest.testContainsObject

java.lang.StackOverflowError
at java.util.regex.Pattern$Loop.match(Pattern.java:4275)
at java.util.regex.Pattern$GroupTail.match(Pattern.java:4227)
at java.util.regex.Pattern$BranchConn.match(Pattern.java:4078)
at java.util.regex.Pattern$CharProperty.match(Pattern.java:3345)
at java.util.regex.Pattern$Branch.match(Pattern.java:4114)
at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168)
at java.util.regex.Pattern$Loop.match(Pattern.java:4295)
...

Turns out this is because of a bug in Sun JDK that will never be fixed:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5050507