Marking methods and classes final

• No extended class can override the method to change its behavior. (This is the final version of that method.)
• A class marked final cannot be extended by any other class (and, all the methods of a final class are implicitly final).
• Security - anyone who uses the class can be sure the behavior will not change (validatePassword example).
• Serious restriction on the use of the class.
• Final simplifies optimizations.