This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
There are (at least) two ways for this:
1) simply look for one capital letter, then use Matcher.find() 4 times
2) use a regular expression that immediately finds the 4th capital letter. You will most likely need a capturing group for that.