Java: OOPs

Adapted with permission from Arnold Rosenbloom, University of Toronto

*added by MisterV

Object Oriented Programming Language:

A programming language which allows the modelling of object interaction

• Java is an OO programming language.
• Typically an OO programming language supports:
  • Encapsulation (via the notion of class)
  • Inheritence: method for extending existing classes by adding methods and fields
  • Polymorphism: Behaviour varies depending on the actual type of an object
• OO Programming Languages encourage code reuse, capturing of concepts

Programming the OO way...

1. Problem solve: Understand a given problem (there is a LOT to this!!) Determine if a solution takes the form of a computer program (and if so)...
2. Create Conceptual Solution: Describe the system to be modelled. That is, give an english description of the system
1. Concepts mapped to OO Paradigm:
   • Think OO: Analyze the problem/solution, view it as a collection of interacting objects, then identify the
     • classes/objects: These are the concepts that need to be captured. Sometimes noun or noun phrases in the above description.
     • methods (RESPONDS-TO): for each class. These are the things that the class can do. Verbs usually identify these in the problem description.
     • attributes (HAS-A): for each class. These are things that each instance has, they define the state of the instance.
     • inheritence (IS-A): classes that this class extends
   • Think Algorithmically: Write algorithms for each of the methods
   1. Java: Translate the above to something the computer can understand (Java)

More about Java:

• a=b calculated by computing the VALUE of the right side and placing it in the left
• Methods in Java pass parameters by VALUE
• Java occasionally garbage collects instances that have no references to them.