This document discusses instantiating objects in object-oriented programming. It explains that a class is a blueprint that can be used to create multiple object instances. An object is created using the "new" operator, which allocates memory for the object and initializes its values. The document provides an example of a Movie class and instantiates three Movie objects with different names, lengths, and directors to demonstrate how object instantiation works.

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

2. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 2
Classes vs. Objects
Instances
 Class = blueprint
 Object
= there can be many
objects of the same
class
= needs to be created
(instantiated)
Movie
name: string
length: int
director: string
Movie()
one
Name: Argo
length: 90
director: Lamont
Movie()
two
name: Titanic
length: 100
director: James
Movie()
three
name: Pride and Prej.
length: 95
director: Ang Lee
Movie()
Instance Variables
Instance Methods
GetName()
GetName()
GetName()
GetName()

3. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 3
Classes vs. Objects
Instances
Movie
Movie()
one
Name: Argo
length: 90
director: Lamont
Movie()
two
name: Titanic
length: 100
director: James
Movie()
three
name: Pride and Prej.
length: 95
director: Ang Lee
Movie()
Instance Variables
Instance Methods
 Instance Variable
= each Instance has variables with
different values
name: string
length: int
director: string
GetName()
GetName()
GetName()
GetName()

4. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 4
Instantiating an Object
one
Name: Argo
length: 90
director: Lamont Johnson
Movie ()
new Operator
= instantiates (creates) an object of a class
= allocates space in the computers memory
GetName()

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Instantiating an Object
new Operator – Android and Java
= instantiates (creates) an object of a class
= allocates space in the computers memory

6. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 6
Instantiating an Object
one
Name: Argo
length: 90
director: Lamont Johnson
Movie ()
Class from which the object is instantiated
Identifier of Object (lower case!)
new Operator
Arguments for Constructor Method
GetName()

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The new Operator
 What is really happening here?
Two spaces in memory are allocated:
 a variable that points (pointer, reference variable) to
an object is created in memory. It stores the address
or reference to the location where the object is stored.
 an object is created in memory.
one
Argo, 90, Lamont Johnson

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The new Operator
 Statement can be split in two!
one Argo, 90, Lamont Johnson

9. ITDP 106 - Information Technology Essentials Elke Vogel-Adham 9
The new Operator
 Instantiating three objects!
one
Argo, 90, Lamont Johnson
two
three
Titanic, 100, James Cameron
Pride and Prejudice, 95, Ang Lee