Computer Science Programming

Object-Oriented Programming

• Problem-solving methodology that produces a solution to a problem in terms of self-contained entities called objects
• Class
  • Description of a group of objects with similar properties and behaviours
    • Any particular object is an instance of a class
    • Contains
      • Fields
        • Named properties
      • Methods
        • Named algorithm defining one aspect of behaviour of a class
        • A function attached to a class
• Object
  • Entity that makes sense within context of a problem
  • Specific, concrete instances of a class
  • Attributes
    • Characteristics that define an object
    • Differentiate objects of the same class
    • Value of attributes is an object's state
• Encapsulation
  • Language feature that enforces hiding information
  • Ability to combine together data and methods of an object
    • Provides an interface so complexities are hidden from a user

Design Methodology

• Brainstorming
  • Local possible classes
• Filtering
  • Find duplicate classes
  • Remove unnecessary classes
• Scenarios
  • Ensure we understand collaborations
  • Assign responsibilities of each class
    • What the tasks are
    • Two types of responsibilities
      • Knowledge
        • What a class must know about itself
        • Behaviour
          • What a class must be able to do
• Responsibility algorithms
  • Design for all actions that classes must exhibit

Inheritance

• Mechanism by which one class acquires the properties (data fields and methods) of another class
• Superclass
  • Class being inherited from
• Derived class
  • Class doing the inheriting