Facade Design Pattern Java Example

 The Facade design pattern provides a simplified interface to a complex subsystem. It creates a single class that acts as a facade, hiding the complexities of the underlying components and providing a unified, easy-to-use interface to the client. 

Here is a Java example demonstrating the Facade pattern with a home theater system:

Java

// Subsystem Components
class DVDPlayer {
    public void on() {
        System.out.println("DVD Player On");
    }

    public void play(String movie) {
        System.out.println("Playing movie: " + movie);
    }

    public void off() {
        System.out.println("DVD Player Off");
    }
}

class Projector {
    public void on() {
        System.out.println("Projector On");
    }

    public void wideScreenMode() {
        System.out.println("Projector in widescreen mode");
    }

    public void off() {
        System.out.println("Projector Off");
    }
}

class SoundSystem {
    public void on() {
        System.out.println("Sound System On");
    }

    public void setVolume(int level) {
        System.out.println("Sound System volume set to " + level);
    }

    public void off() {
        System.out.println("Sound System Off");
    }
}

// Facade Class
class HomeTheaterFacade {
    private DVDPlayer dvdPlayer;
    private Projector projector;
    private SoundSystem soundSystem;

    public HomeTheaterFacade(DVDPlayer dvdPlayer, Projector projector, SoundSystem soundSystem) {
        this.dvdPlayer = dvdPlayer;
        this.projector = projector;
        this.soundSystem = soundSystem;
    }

    public void watchMovie(String movie) {
        System.out.println("Get ready to watch a movie...");
        projector.on();
        projector.wideScreenMode();
        soundSystem.on();
        soundSystem.setVolume(10);
        dvdPlayer.on();
        dvdPlayer.play(movie);
    }

    public void endMovie() {
        System.out.println("Shutting down home theater...");
        dvdPlayer.off();
        soundSystem.off();
        projector.off();
    }
}

// Client Code
public class FacadePatternDemo {
    public static void main(String[] args) {
        DVDPlayer dvdPlayer = new DVDPlayer();
        Projector projector = new Projector();
        SoundSystem soundSystem = new SoundSystem();

        HomeTheaterFacade homeTheater = new HomeTheaterFacade(dvdPlayer, projector, soundSystem);

        homeTheater.watchMovie("The Matrix");
        System.out.println("\n");
        homeTheater.endMovie();
    }
}

In this example:

• Subsystem Components:

  DVDPlayer, Projector, and SoundSystem represent the complex parts of the home theater system, each with its own specific methods.
• Facade Class:

  HomeTheaterFacade acts as the facade. It encapsulates the interactions with the subsystem components. Methods like watchMovie() and endMovie() provide a simplified interface to the client, handling the orchestration of multiple component actions internally.
• Client Code:

  The FacadePatternDemo class demonstrates how a client interacts only with the HomeTheaterFacade to perform complex operations like watching or ending a movie, without needing to know the intricate details of each individual component.