Chapter 12 : Review Question

Q6 : Describe a situation where dynamic binding is a great advantage over its absence.

A : There is a base class, A, that defines a method draw that draws some figure associated with the base class. A second class, B, is defined as a subclass of A. Objects of this new class also need a draw method that is like that provided by A but a bit different. With overriding, we can directly modify B’s draw function. But without it, we either make a specific function in A for B and inherit it.

Q7 : What is a virtual method?

A : A virtual method is a declared class method that allows overriding by a method with the same derived class signature. Virtual methods are tools used to implement the polymorphism feature of an object-oriented language, such as C#. When a virtual object instance method is invoked, the method to be called is determined based on the object's runtime type, which is usually that of the most derived class.

Q8 : What is an abstract method? What is an abstract class?

A : An abstract method is a method which all descendant classes should have. An abstract class is a class which has abstract method.

Q9 : Describe briefly the eight design issues used in this chapter for object-oriented languages.

A :

-What non-objects are in the language?

-Are Subclasses Subtypes? If so, derived objects can be legally used wherever a parent object could be used.

-Type Checking and Polymorphism

-Single and Multiple Inheritance. Inherit from 1 (or more than 1) parent.

-Object Allocation and Deallocation.  Are objects allocated from heap or stack.

-Dynamic and Static Binding. When are messages bound to methods, before or during run-time?

-Nested Classes. Can a class be nested inside another class?

-Initialization of Objects. Are objs init'd when created? Implicit or explicit?

Q10 : What is a nesting class?

A : A nesting class is a class defined inside another class.