OOP (Object Oriented Programming)

OOP (Object Oriented Programming)

1. Class

   • Description of how objects should be treated.
   • Describes how data is stored
   • Describes the methods executed on that data
   • Static: Associated with the class. (Runs the same regardless of data).

2. Object

   • A specific instance of a class
   • Specific instances of data and methods
   • Non-Static: Associated with the object (Needs an object to be initialized).
   • This: Changes data within object. this.numPeople = 2; means this objects numPeople attribute should be set to 2

3. Attributes

   • What is stored in the object
   • Attributes should never be public always private.

4. Behvaiours

   • What is done with the object (the methods)
   • Typically operations on the data
   • Methods can be overloaded. i.e. the method is the same but it has different parameters

5. Constructors

   • Initalises object

6. Reference

   • Something is passed by reference if the method is simply given a reference (essentially a location) to the data rather than the data itself
   • All capital letter data types are references.

7. Inheritance

   • Relationships between classes. Used to create more specific versions of classes
   • Superclass: The parent of a class is referred to as a superclass.
     • Stores data and methods common to all subclasses
     • Can also implement default behaviours that can be overwritten
     • Protected methods and attributes are available to all subclasses
   • Subclass: The child of a superclass. A more specific version of a superclass. I.e. What a bike is to a vehicle
     • Inherits methods and attributes of superclass
     • Can add additional attributes and methods
     • Can overwrite behaviours of the superclass
     • super keyword refers to instance of superclass can be used to run methods and for initalisation
     • extends keyword used to state the superclass of a subclass: Bike extends Vehicle