7.7. Exercises
Test yourself: run through the following list of OO terms—some formal, some informal—and see whether you can define each term in your own words without referring to the text:
Abstract class Class Derived class Abstract method Class hierarchy Dictionary Abstraction Class variable Encapsulation Accessor (of a property) Classification Field Accessor method Client (object) Generalization Aggregation Client code Generic class Ancestor class Collection class Get accessor Association Composite class Get method Base class Constant Getter Behavioral relationship Constructor Information hiding Binary association Delegation Inheritance Instance Operation Set method Instance variable Ordered list Setter Instantiation Overloading Sibling class Interface Overriding Simple type Local variable Parent class Sorted ordered list Leaf node Polymorphism Specialization Link Predefined type State Member Private accessibility Static field Method Public accessibility Static method Method header Reference Static variable Method signature Reference variable Structural relationship Modeling Reflexive association Supplier (object) Multiple inheritance Root (of a class hierarchy) Unary association Multiplicity Set (collection) User-defined type Object (in the software sense) Set accessor Which fields, belonging to which SRS classes, might be well suited to being declared as static?
It has been argued that the capability to declare and implement interfaces in the C# language eliminates the need for derived classes to inherit from multiple base classes. Do you agree or disagree? Why? Can you think of any ways in which implementing multiple interfaces "falls short" as compared with true multiple inheritance?
The following client code scenarios would each cause compilation errors—can you explain why this is so in each case? Be as precise as possible as to the reasons—they might not be as obvious as first meets the eye!
Assume that Professor and StudentTeacher are both classes that implement the ITeacher interface.
Scenario #1:
Professor p; StudentTeacher s = new StudentTeacher(); ITeacher t; t = s; p = t;
Scenario #2:
Professor p = new Professor(); StudentTeacher s; ITeacher t = new StudentTeacher(); s = t;
Scenario #3:
Professor p = new Professor(); StudentTeacher s = new StudentTeacher(); ITeacher t; p = t;