What is a user-defined exception?
– Apart from the exceptions already defined in Java package libraries, user can define his own exception classes by extending Exception class. • Describe the visitor design pattern? – Represents an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates. The root of a class hierarchy defines an abstract method to accept a visitor. Subclasses implement this method with visitor.visit(this). The Visitor interface has visit methods for all subclasses of the baseclass in the hierarchy.
