Chapter 4: "Objects and Classes"

Chapter 4: "Objects and Classes"

1. OOP: Object Oriented Programming

   • Using models to solve real problems

2. Object

   • Every object has two features
     • Attributes
       • In Java: Fields
     • Actions the object is able to perfrom
       • In Java: Methods
   • AKA: Instance
   • No value: null

3. Classes

   • Blueprint needed to create objects of identical type
   • Class determines the object
   • Let programmers create abstraction of a problem
     • Abstraction: Using programming objects to represent real-world objects
   • All elements in Java must reside in a class
   • 3 things to consider when writing a class
     • Class name
     • Fields
     • Methods
   • Keyword: class
   • Every class must have a constructor.
     • Used to construct an object.
     • AKA: "constructor method"
     • Does not have return value

4. Fields

   • Primative or reference variables

5. Methods

   • Define actions objects can do
   • Declaration + Body
     • Declaration: Return value, method name, list of arguments
       • Void: Method returns nothing
     • Body: code to perform that action
   • Main: entry point to application

6. UML: Unified Modeling Language

   • UML class diagram
   • Allows you to include field type and method signature.