Classes

• What is a Class? #1

  • Classes are used as blueprints or templates that can be used to create objects within Object Oriented Programming or OOP 
  • An object is created from a specific instance of a class and has its own state and behaviours 
  • Using this method allows for reusable and organised code in a modular way 
  • Consider a class of students 
  • Each student has a name, a date of birth and gender 
  • Therefore we can create a blueprint or template for all students by making a class which contains these three attributes 
• What is a Class? #2

  • As each student (or object) is created they will each have their own name, date of birth and gender attributes along with their own state for example 
  • Name “John” 
  • Date of birth “06/10/2015” 
  • Gender “Male” 
  • Some classes are already prebuilt into a programming language saving the developer from having to write them from scratch and often provide common functionality 
• • Examples from Java include: 
  • Date and calendar when working with dates 
  • String when working with strings of text 
  • Random when generating random numbers 
  • Scanner when reading input from a user or file 
• What is a class? #3

  • Custom classes are created by the programmer to define new data types 
  • For example, a class for animals does not exist and so the programmer must define a custom class 
  • Instantiation is the term used for creating an object from a class 
  • Each class contains attributes which are essentially variables within a class and are also known as Class Variables 
  • Objects that are created from a class contain attributes which are also known as instance variables
• • What are classes? #3
  • Classes can also contain methods/functions/procedures 
  • Methods are actions or behaviours that can be performed 
  • The name that is used to refer to an object is known as the identifier 
  • Below is a visual representation of both a class and objects that have been instantiated
• Classes image