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
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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
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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
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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