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.
As you said, sleep() is a static method. It causes the current thread to sleep for a period of time. It always refers to the current thread. It doesn't matter if you invoke it using the class name or an instance of the class, it will always cause the current thread to sleep.