CS Classroom: Object-Oriented Programming in Java (Option D - IB Computer Science, SL)

Introduction

• Purpose: Cover SL content for Option D in IB Computer Science.
• Focus: Understanding object-oriented programming (OOP) deeply and intuitively.
• Structure: Basics of programming languages, scenario-based OOP program development, theoretical content, tasks in Java OOP, and code descriptions.

Modern Programming Languages

• Examples: Java, C++, Python
• Common Features:
  • Unicode: Enables use of various symbols and text output.
  • Portability: Programs can run on different OS (Linux, Windows).
  • Abstraction: Simplified representation of complex processes, mimicking real life.

Coding Style and Naming Conventions

• Best Practices:
  • Indentation
  • Comments
  • Meaningful variable and method names
• Benefits:
  • Easier team collaboration and understanding.
  • Simplifies debugging.

Object-Oriented Programming Overview

• Purpose: Model the real world by categorizing data and defining related methods and attributes.
  • Class: Template for objects (e.g., Employee class).
  • Object: Instance of a class.
• Attributes and Behaviors: Variables and methods associated with objects.

Scenario: Los Pollos Fast Food Chain

• Goal: Implement a software system to track employees.
  • Employee Class: Defined with attributes (e.g., name, employeeID, salary, complaints) and methods (constructors, mutators, accessors).
  • Instantiation: Creating objects from classes.

Key Concepts and Syntax

• Class Definition: public class Employee {}
  • Attributes: String name; int employeeID; double salary; String[] complaints;
  • Constructor: Initializes new objects.
  • Methods (Mutators, Accessors)
    • Example: public void setSalary(double salary) {...}

Creating and Using Classes

• Example: Creating an employee object Employee emp1 = new Employee("Walter", 356, 1000000); emp1.addComplaint("Scarily smart"); System.out.println(emp1.getSalary());

Inheritance

• Purpose: Create specialized subclasses from a superclass.
• Syntax: public class Salesman extends Employee {}
• Example: Salesman inherits Employee attributes and methods, adds specific functionality public class Salesman extends Employee { private double commissionRate; // Constructors and additional methods here }

Aggregation

• Purpose: One class contains objects of another class.
• Example: A Salesman having multiple Sale objects. public class Salesman { private Sale[] sales = new Sale[10]; // Methods to add and manage sale objects }

Polymorphism and Method Overloading/Overriding

• Polymorphism: Methods in different forms.
  • Method Overloading: Same method name, different parameters within the same class.
  • Method Overriding: Same method name in superclass and subclass.

Libraries

• Purpose: Reusable code, saves development time.
• Usage: Java standard libraries (import java.util.*;) and third-party libraries.*

Encapsulation

• Purpose: Hide internal object details, control access.
• Access Modifiers: private, protected, public
• Example: Private attributes with public accessors and mutators private double salary; public double getSalary() { return this.salary; } public void setSalary(double salary) { if(salary > 0) { this.salary = salary; } }

Static Methods and Attributes

• Purpose: Belong to the class rather than instances.
• Example: Utility methods public static double calculateNetSalary(double salary, double taxRate) {...} Employee.calculateNetSalary(40000, 0.25);

Modularity

• Purpose: Breaking down programs into smaller, manageable pieces.
• Benefits: Easier maintenance, debugging, reusability.

Graphical Representation: UML Diagrams

• Components: Class names, attributes, methods.
• Example: Employee and Salesman UML diagrams.

Exam Example: Restaurant Management System

• Scenario: Tables, payments, food/drink items.
• Code snippets: Add food/drink items, calculate bill.

Pros and Cons of OOP

• Pros: Modularity, encapsulation, inheritance (code reuse, maintenance).
• Cons: Not suitable for small projects, more memory usage, time-consuming.

Key Terms

• Identifier: Variable, method, or class names.
• Object Reference: Variable containing the object's memory address.
• Method Signature: Method return type, name, and parameters.

Conclusion

• This content is crucial for performing well in the IB Computer Science SL exam.
• Overview of critical OOP concepts, practical implementations, and theoretical understanding.