Steps to reproduce:
1. see http://stackoverflow.com/questions/13479021/double-checked-locking-disappeared-from-checkstyle-why
2. In IDE of your choice, with latest Checkstyle installed, configure IDE to point at matterhorn-checkstyle.xml. In my case, with Intellij IDEA, I get plugin error reporting "remove DoubleCheckedLocking from config file"
3. Once DoubleCheckedLocking is removed from file all is good
Expected Results: Happy checkstyle in IDE