Description: One of the nice things about programming in Java is that the language and its class library are designed to provide practical solutions to real object-oriented programming problems. In the object programming community, many of these solutions have been well documented as design patterns; each pattern is a generic solution to a common problem. One such pattern is known as the Observer pattern, which is a solution to the updating problem that arises when some objects have a dependency relationship with others. Java provides a ready-made implementation for this pattern through the Observable class and the Observer interface.
