Ch 8

Question 1

Inheritance

Answer 1

The property that instances of a child class (or subclass) can access both data and behavior (methods) associated with a parent class (or superclass).

Question 2

Extension

Answer 2

Inheritance means that the behavior and data associated with child classes are always an extension (i.e. a larger set) of the properties associated with the parent classes. A subclass will have all the properties of the parent class and other properties as well.

Question 3

Contraction

Answer 3

Since a child class is a more specialized (or restricted) form of the parent class, it is also, in a certain sense, a contraction of the parent type.

Question 4

Reasons to use inheritance

Answer 4

There are two main reasons to use inheritance:

1) . Inheritance as a means of code reuse. Because a child class can inherit behavior from a parent class, the code does not need to be rewritten for the child.
2) . Inheritance as a means of concept reuse. This occurs when a child class overrides behavior defined in the parent. Although no code is shared between the parent and child, the child and parent share the definition of the method.

Question 5

Subclassing for specialization

Answer 5

The child class is a special case of the parent class; in other words, the child class is a subtype of the parent class.

Question 6

Subclass for specification

Answer 6

The parent class defines behavior that is implemented in the child class but not in the parent class.

Question 7

Subclass for construction

Answer 7

The child class makes use of the behavior provided by the parent class but is not a subtype of the parent class.

Question 8

Subclass for generalization

Answer 8

The child class modifies or overrides some of the methods of the parent class.

Question 9

Subclass for extension

Answer 9

The child class adds new functionality to the parent class but does not change any inherited behavior.

Question 10

Subclass for limitation

Answer 10

The child class restricts the use of some of the behavior inherited from the parent class.

Question 11

Subclass for variance

Answer 11

The child class and parent class are variants of each other, and the class-subclass relationship is arbitrary.

Question 12

Subclass for combination

Answer 12

The child class inherits features from more than one parent class. This is multiple inheritance.

Question 13

Singleton

Answer 13

An object that there only ever will be one instance of within a program.

Question 14

Benefits of inheritance

Answer 14

Software reusability, code sharing, consistency of interface, software components, rapid prototyping, polymorphism & frameworks, information hiding.

Question 15

Costs of inheritance

Answer 15

Execution speed, program size, message-passing overhead, program complexity.