This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma 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.