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.
You use it exactly as you wrote it. dateString is the date you want to check. If the date can not be converted into a valid date, it throws a parse exception. If you want the date to be in a specific format in order to be determined to be valid then you can use the SimpleDateFormat class to define a format.