📚 Week 3

📝 ArrayList

Creating an ArrayList

• Declare and Instantiate an ArrayList:

  ArrayList<String> kombuchaFlavors = new ArrayList<>();

Basic Operations

• Add Elements:

  kombuchaFlavors.add("Ginger-Lemon");
  kombuchaFlavors.add("Blueberry-Basil");
  kombuchaFlavors.add("Raspberry-Lime");

• Access Elements:

  String favoriteFlavor = kombuchaFlavors.get(0); // Accesses the first element, "Ginger-Lemon"
  System.out.println("Favorite flavor: " + favoriteFlavor);

• Modify Elements:

  kombuchaFlavors.set(0, "Mango-Ginger"); // Updates "Ginger-Lemon" to "Mango-Ginger"

• Remove Elements:

  kombuchaFlavors.remove("Blueberry-Basil"); // Removes "Blueberry-Basil" from the list

• Iterate Over ArrayList:

  System.out.println("Available Flavors:");
  for (String flavor : kombuchaFlavors) {
      System.out.println(flavor);
  }

🎮 Practical Exercise: Videogame Shop Inventory

• Task: Use ArrayList to manage a videogame shop's inventory.
• Instructions:
  • Write a Java class, VideogameShop, and implement functionalities to:
    • Add new videogame titles to the inventory.
    • Remove titles no longer available.
    • Update titles.
    • Retrieve and display all available titles.
  • Bonus: Implement a search feature to find a videogame by name.

💡 Discussion

• Reflect on the ease of using ArrayList compared to traditional arrays for managing changing data.

🔧 Interfaces

Understanding Interfaces

• Define and Declare an Interface:

  public interface Vehicle {
      int MAX_SPEED = 120; // Static variable
      void start();
      void stop();
      default void displayType() {
          System.out.println("This is a vehicle.");
      }
  }

Basic Operations

• Implement an Interface:

  public class Car implements Vehicle {
      @Override
      public void start() {
          System.out.println("Car starts with a key.");
      }
  
      @Override
      public void stop() {
          System.out.println("Car stops when brakes are applied.");
      }
  }

• Access Interface Methods and Static Variables:

  Vehicle myCar = new Car();
  myCar.start(); // Calls the start method defined in Car
  myCar.stop(); // Calls the stop method defined in Car
  System.out.println("Maximum speed: " + Vehicle.MAX_SPEED); // Accessing the static variable

• Extend Interface Functionality:

  public interface ElectricVehicle extends Vehicle {
      void chargeBattery();
      default void displayBatteryStatus() {
          System.out.println("Battery status: Good");
      }
  }

• Implement Extended Interface:

  public class ElectricCar implements ElectricVehicle {
      @Override
      public void start() {
          System.out.println("Electric car starts silently.");
      }
  
      @Override
      public void stop() {
          System.out.println("Electric car uses regenerative braking to stop.");
      }
  
      @Override
      public void chargeBattery() {
          System.out.println("Charging the battery.");
      }
  }

🎵 Practical Exercise: Music Streaming Service

• Task: Use interfaces to develop components for a music streaming service.
• Instructions:
  • Write Java classes to simulate a music streaming service:
    • Define interfaces: Playable for media playback functions and PlaylistManager for managing playlists.
    • Implement the interfaces in classes like Song, Album, and UserPlaylist.
    • Instantiate these classes in a main program to simulate interacting with the streaming platform.
    • Use default methods for common functionalities and static variables for settings.
  • Challenge: Enhance the Playable interface with a default method to increase or decrease volume.

💡 Discussion

• Reflect on the practical use of interfaces in building modular and scalable applications.
• Discuss how interfaces facilitate the development of flexible and extensible software architecture.

🔍 Abstract Classes

Understanding Abstract Classes

• Define and Declare an Abstract Class:

  public abstract class Person {
      protected String name;
      protected int age;
  
      public Person(String name, int age) {
          this.name = name;
          this.age = age;
      }
  
      // Abstract method that subclasses must implement.
      public abstract void introduce();
  
      // Concrete method with implementation.
      public void displayInfo() {
          System.out.println("Name: " + name + ", Age: " + age);
      }
  }

Basic Operations

• Extend an Abstract Class:

  public class Student extends Person {
      private String studentID;
  
      public Student(String name, int age, String studentID) {
          super(name, age);
          this.studentID = studentID;
      }
  
      @Override
      public void introduce() {
          System.out.println("Hi, I am student " + name + ", and my ID is " + studentID);
      }
  }
  
  public class Instructor extends Person {
      private String employeeID;
  
      public Instructor(String name, int age, String employeeID) {
          super(name, age);
          this.employeeID = employeeID;
      }
  
      @Override
      public void introduce() {
          System.out.println("Hello, I am instructor " + name + ", and my employee ID is " + employeeID);
      }
  }

👨‍🍳 Practical Exercise: Culinary School Management System

• Task: Use abstract classes to design and simulate a culinary school management system.
• Instructions:
  • Write Java classes that extend the abstract classes Person and Course, representing different roles and courses in the culinary school.
    • Define another abstract class: Course with a method template for course activities.
    • Implement the abstract classes in specific courses like Baking and CulinaryBasics.
    • Instantiate these classes to demonstrate the management and operations of the culinary school.

💡 Discussion

• Reflect on the benefits of using abstract classes to establish a common structure while allowing flexibility for specific implementations.
• Discuss how abstract classes provide a solid foundation for building scalable and adaptable systems in educational environments.

💰 BigDecimal

Understanding BigDecimal

• Define and Declare BigDecimal:
  • BigDecimal allows for high-precision arithmetic in Java, crucial for applications requiring exact calculations, such as financial contexts.

  import java.math.BigDecimal;

Basic Operations

• Create BigDecimal Instances:

  • Instantiate BigDecimal objects from strings to avoid precision loss.

  BigDecimal balance = new BigDecimal("12345.67");
  BigDecimal interestRate = new BigDecimal("0.05");

• Perform Arithmetic Operations:

  • Use BigDecimal for precise arithmetic operations necessary in financial applications.

  BigDecimal interest = balance.multiply(interestRate);
  System.out.println("Interest: " + interest);

• Scaling and Rounding:

  • Handle scaling and rounding with BigDecimal to ensure results meet financial standards.

  BigDecimal roundedInterest = interest.setScale(2, BigDecimal.ROUND_HALF_UP);
  System.out.println("Rounded Interest: " + roundedInterest);

🏦 Practical Exercise: Simple Banking Application

• Task: Use BigDecimal to simulate a simple banking application that handles deposits, withdrawals, and interest calculations.
• Instructions:
  • Write Java classes that utilize BigDecimal to ensure precise handling of financial transactions.
    • Define a BankAccount class to represent a bank account where each operation on the account balance must be done using BigDecimal.
    • Instantiate BankAccount and simulate various transactions to demonstrate how BigDecimal handles financial data precisely.

💡 Discussion

• Reflect on the importance of using BigDecimal in applications requiring high precision to prevent common floating-point errors.
• Discuss the critical role of BigDecimal in financial systems where the accuracy of calculations can impact financial stability and compliance with legal standards.