Facade

• Is a Structural Design Pattern
• Facade provides a simple, unified interface to a complex subsystem
• It hides the complexity and gives you a single easy entry point
• Create one class that:
  • Knows the subsystem
  • Coordinates the calls
  • Exposes a simple API

When to use?

• Subsystem is complex
• Client code is messy
• For loose coupling
• To expose a clean API

class CarFacade {
    private Engine engine = new Engine();
    private FuelInjector injector = new FuelInjector();
    private AirFlowController airFlow = new AirFlowController();

    void startCar() {
        engine.start();
        injector.inject();
        airFlow.control();
        System.out.println("Car started");
    }
}

public class Client {
    public static void main(String[] args) {
        CarFacade car = new CarFacade();
        car.startCar();
    }
}