Structural Pattern

Facade Pattern

Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.

8 min readHigh Priority

1What is Facade Pattern?

Real-World Analogy

Hotel Concierge

Instead of dealing with housekeeping, restaurant, taxi, and tour services separately, you just tell the concierge what you need. They handle all the complex coordination behind the scenes.

Computer Power Button

One button starts CPU, memory, disk, BIOS, OS - a complex boot sequence. The power button is a facade hiding all that complexity.

Facade provides a simplified interface to a complex subsystem. It doesn't add functionality - it just makes the existing functionality easier to access by hiding the complexity.

Facade Pattern Structure

Facade provides simple interface while delegating work to subsystem classes.

2Facade vs Other Patterns

Pattern	Intent	Interface
Facade	Simplify complex subsystem	New simpler interface
Adapter	Make incompatible interfaces work	Convert existing interface
Decorator	Add behavior dynamically	Same interface, enhanced
Proxy	Control access to object	Same interface

3Implementation

Facade Pattern - Home Theater System

// ========== Complex Subsystem Classes ==========
class Amplifier {
    public void on() { System.out.println("Amplifier on"); }
    public void off() { System.out.println("Amplifier off"); }
    public void setVolume(int level) { System.out.println("Volume: " + level); }
    public void setSurroundSound() { System.out.println("Surround sound on"); }
}

class DVDPlayer {
    public void on() { System.out.println("DVD Player on"); }
    public void off() { System.out.println("DVD Player off"); }
    public void play(String movie) { System.out.println("Playing: " + movie); }
    public void pause() { System.out.println("Paused"); }
    public void stop() { System.out.println("Stopped"); }
}

class Projector {
    public void on() { System.out.println("Projector on"); }
    public void off() { System.out.println("Projector off"); }
    public void wideScreenMode() { System.out.println("Widescreen mode"); }
}

class Lights {
    public void dim(int level) { System.out.println("Lights dimmed to " + level + "%"); }
    public void on() { System.out.println("Lights on"); }
}

class Screen {
    public void down() { System.out.println("Screen lowered"); }
    public void up() { System.out.println("Screen raised"); }
}

// ========== Facade ==========
class HomeTheaterFacade {
    private Amplifier amp;
    private DVDPlayer dvd;
    private Projector projector;
    private Lights lights;
    private Screen screen;
    
    public HomeTheaterFacade(Amplifier amp, DVDPlayer dvd, 
            Projector proj, Lights lights, Screen screen) {
        this.amp = amp;
        this.dvd = dvd;
        this.projector = proj;
        this.lights = lights;
        this.screen = screen;
    }
    
    // Simple unified interface
    public void watchMovie(String movie) {
        System.out.println("\n=== Get ready to watch a movie ===");
        lights.dim(10);
        screen.down();
        projector.on();
        projector.wideScreenMode();
        amp.on();
        amp.setVolume(5);
        amp.setSurroundSound();
        dvd.on();
        dvd.play(movie);
    }
    
    public void endMovie() {
        System.out.println("\n=== Shutting down ===");
        dvd.stop();
        dvd.off();
        amp.off();
        projector.off();
        screen.up();
        lights.on();
    }
}

// ========== Client Code ==========
public class Main {
    public static void main(String[] args) {
        // Create subsystem components
        Amplifier amp = new Amplifier();
        DVDPlayer dvd = new DVDPlayer();
        Projector proj = new Projector();
        Lights lights = new Lights();
        Screen screen = new Screen();
        
        // Create facade
        HomeTheaterFacade homeTheater = new HomeTheaterFacade(
            amp, dvd, proj, lights, screen);
        
        // Simple interface - one method does it all!
        homeTheater.watchMovie("Inception");
        
        // Later...
        homeTheater.endMovie();
    }
}

Output:

=== Get ready to watch a movie ===
Lights dimmed to 10%
Screen lowered
Projector on
Widescreen mode
Amplifier on
Volume: 5
Surround sound on
DVD Player on
Playing: Inception

4Real-World Applications

Spring JdbcTemplate

Simplifies JDBC operations - connection, statement, result handling in one call.

SLF4J Logger

Simple logging interface hiding Log4j, Logback complexity.

Compiler

compile() method hides lexer, parser, optimizer, code generator.

Payment Processing

ProcessPayment() hides validation, fraud check, gateway, notification.

5Interview Follow-up Questions

Interview Follow-up Questions

Common follow-up questions interviewers ask

6Key Takeaways

1Facade provides a simple interface to a complex subsystem.

2It coordinates subsystem calls but doesn't add behavior.

3Clients can still access subsystem directly if needed.

4Different from Adapter (simplifies vs converts interface).

5Common in: compilers, frameworks, payment systems, ORMs.

6Promotes loose coupling between clients and subsystems.