Java Object-Oriented Programming Lecture Notes

Introduction

• Course will not cover Java basics.
• Recommended Resources:
  • YouTube Java series
  • O'Reilly's object-oriented programming with Java course
  • These resources go in more depth than the class videos.

Tools and Sponsors

• IntelliJ: Recommended editor.
• DiffBlue: Sponsor offering AI-powered unit test generation for Java.
  • Free community edition available as IntelliJ plugin.
  • Offers automatic test generation to improve test coverage.
  • Free license upgrade for viewers.

Java Basics Review

• Project Setup: Assumes knowledge of creating and running Java projects.
• Main Method: Entry point of Java applications.
  • public static void main(String[] args)
  • Use of System.out.println() to print "Hello World".
• Classes and Methods
  • Everything defined within a class.
  • println method invocation with arguments.
  • Difference between parameters (method definition) and arguments (method invocation).

Object-Oriented Concepts

• Class and Object
  • Class: Blueprint for creating objects.
  • Object: Instance of a class.
• Static Variables and Methods
  • Static means no need to create an instance of the class.
  • Example: System.out is a static variable for println.

Creating and Using Classes

• Creating a Class:
  • Example: Creating a User class.
  • Class as a 'cookie cutter' for objects.
• Instantiating Objects
  • Syntax: User u = new User();
  • Constructor: Method-like structure used to create objects.

Attributes and Variables

• Adding Attributes to a Class:
  • Example: String name; and String membership;
  • Assign values to attributes: u.name = "Caleb";
• Accessing Attributes
  • Use dot operator: u.name

Object-Oriented Programming Principles

• Encapsulation
  • One of the main pillars of OOP.
  • Emphasizes restricting direct access to some of an object's components.

Practical Examples

• Creating Multiple Objects
  • Example: Creating multiple User objects with different attributes.
  • Printing attributes using System.out.println().
• Default Values
  • Strings default to null.
  • Primitives (e.g., int) default to zero.

Conclusion

• Objects help organize code to match domain/business requirements.
• OOP provides a structured way to model real-world entities.