Lakhasly

TOPICS
Class basics:
Defining and using a class Access identifiers
Set/get methods
Data initialization
What is a constructor?
Defining constructors
Overloading constructor Usingthisreference
Dr. MFH, 2022
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IN JAVA
Everything must be in a class. There are no global functions or global data.
Even Main ............ is a Class
Dr. MFH, 2022
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What Is A Class?
Let’s start by an example:
• Properties: – Name
– Age
– Breed
– Favorite Food
• Behaviors:
– Make meow sound
– Play – Wash – Eat – Hunt
Dr. MFH, 2022
4
Copyright 2017, Oracle and/or its affiliates. All rights reserved.

What Is A Class?
The combination of properties and behaviors is ... – Called a class
– A blueprint or recipe for an object
– Usedtocreateobjectinstances
Object instances
Cat class -Properties -Behaviors
Dr. MFH, 2022
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Copyright 2017, Oracle and/or its affiliates. All rights reserved.

Creating New Instances From A Blueprint → Objects Cat class
Properties
• name
• age
• favoriteFood
Behaviors • meow
• play
• eat
cat1 • "Opal"
• 11
• "Mice"
cat2 • "Misty"
• 5
• "Chicken"
cat3 • "Tiger"
• 15
• "BlueJ"
Dr. MFH, 2022
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Copyright 2017, Oracle and/or its affiliates. All rights reserved.

So............Object-Oriented Programming
• Interaction of objects • No arranged sequence
Dr. MFH, 2022
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Copyright 2017, Oracle and/or its affiliates. All rights reserved.

So............A Class :
– Is a blueprint or recipe for an object
– Describes an object’s properties (data types) and behaviors
(operations)
– Is used to create Object instances
Class -Properties -Behaviors
Object instances
Dr. MFH, 2022
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Copyright 2017, Oracle and/or its affiliates. All rights reserved.

To better understand:
Let’s consider an online shopping cart scenario. Imagine an online store called Duke’s Choice.
(1) One shopper is Duke’s mother, Mrs. Duke. As she shops, she places items in a shopping cart, she places shirts.
(2) After she fills the cart, she checks out.
(3) The checkout process applies the purchase to a credit card, which is verified, (4) and then Mrs. Duke receives an order number so that she can track her order or return it.
As a software developer, when you are presented with this scenario such as Duke’s Choice for an application that you need to develop, you can analyze the scenario by breaking it into steps and defining the objects of the scenario.
Dr. MFH, 2022
9
Copyright 2017, Oracle and/or its affiliates. All rights reserved.

To better understand:
Dr. MFH, 2022
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Copyright 2017, Oracle and/or its affiliates. All rights reserved.

To better understand:
To validate objects in such a problem domain you identify the properties of all objects:
• Objects are physical or conceptual.
Physical: Shirt
Conceptual: Online Account Or Credit Card
Dr. MFH, 2022
11
Copyright 2017, Oracle and/or its affiliates. All rights reserved.

To better understand:
• Objects have properties that represent the state of the object:
– Size – Price – Color
Color property value is red.

Copyright 2017, Oracle and/or its affiliates. All rights reserved.

To better understand:
• Objects have behaviors (things they can do) : – Shop
– Put item in cart –Pay