Week 6

1. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 1
Inheritance
CIS 2403
Object Oriented Programming

2. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 2
Association
Program Class instantiates in the Main methods
an object one from the Movie class
Until now …. Only Association
Progam
Main()
one
Name: Argo
length: 90
director: Lamont Johnson
Movie()

3. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 3
Inheritance
Inheritance
= your object’s family tree
 used to avoid duplicate
code
 to save time in coding
 to reduce chances of
errors

4. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 4
Inheritance
Important terms:
– Base class: class used as the
basis for inheritance (Vehicle)
– Base class = superclass
= parent class
– Derived class: a class that
inherits form a base class
– Derived class = extended class
= subclass
= child class
– Ancestors = entire list of parent
classes
– Descendants = entire list of child
classes

5. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 5
Inheritance
 Use extends to inherit from a base class!
 The arrow stands for inheritance!
Person
firstName: string
lastName: string
Person()
Display()
PartTime
room: string
PartTime()
Display()
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

6. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 6
Inheritance
Methods can be overriden by the subclass
 use virtual (parent class) and override (child class)
Person
firstName: string
lastName: string
Person()
Pay()
Faculty
room: string
Faculty()
Pay()
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

7. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 7
Inheritance
Constructors
 when the base class has a constructor, your subclass
needs one, too.
 use super to connect to base class constructor
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

8. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 8
Inheritance
 Access Modifier: protected
 Can be accessed in the class and in the
sub class
Person
firstName: string
lastName: string
Person()
Display()
Faculty
room: string
Faculty()
Display()
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

9. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 9
Accessing the base class
The Super Keyword
 Sometimes you want to use the parent
class method that is overriden by the
child class method
 Use the keyword “super” for accessing
the base Class method
 Example: base.Display()
Person
firstName: string
lastName: string
Person()
Display()
Faculty
room: string
Faculty()
Display()
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

10. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 10
Abstract Class
Abstract class
 a class that is never instantiated
 you must create a subclass that
inherits from the superclass
 abstract classes have abstract
members that the derived class must
override to provide functionality
Person
firstName: string
lastName: string
Person()
Display()
Faculty
room: string
Faculty()
Display()
Employee
empNumber: int
empName: string
empHours:double
Employee()
Pay()
PartTime
hourlyRate: int
PartTime()
Pay()

11. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 11
Abstract Class
Abstract class  ExampleVehicle
Price: double
Year: int
Vehicle ()
showDetail()
Car
EngineSize: double
Car()
showDetail()