Pola Metode Templat dan Keadaan

public abstract class BeverageMaker {

  // The template method - defines the algorithm's skeleton
  public final void prepareBeverage() {
    boilWater();
    brew();
    pourInCup();
    addCondiments();
  }

  // Common steps
  private void boilWater() {
    System.out.println("Boiling water");
  }

  private void pourInCup() {
    System.out.println("Pouring into cup");
  }

  // Abstract steps - must be implemented by subclasses
  protected abstract void brew();
  protected abstract void addCondiments();
}

public class CoffeeMaker extends BeverageMaker {
  @Override
  protected void brew() {
    System.out.println("Dripping coffee through filter");
  }

  @Override
  protected void addCondiments() {
    System.out.println("Adding sugar and milk");
  }
}

public class TeaMaker extends BeverageMaker {
  @Override
  protected void brew() {
    System.out.println("Steeping the tea bag");
  }

  @Override
  protected void addCondiments() {
    System.out.println("Adding lemon");
  }
}

public class Main {
  public static void main(String[] args) {
    System.out.println("--- Making Coffee ---");
    BeverageMaker coffee = new CoffeeMaker();
    coffee.prepareBeverage();

    System.out.println("\n--- Making Tea ---");
    BeverageMaker tea = new TeaMaker();
    tea.prepareBeverage();
  }
}

// State Interface
interface LightState {
  void handleRequest(TrafficLight light);
  String getStateName();
}

// Concrete State: Red Light
class RedLightState implements LightState {
  @Override
  public void handleRequest(TrafficLight light) {
    System.out.println("Red light: STOP!");
    light.setState(new GreenLightState()); // Transition to Green
  }

  @Override
  public String getStateName() {
    return "Red";
  }
}

// Concrete State: Green Light
class GreenLightState implements LightState {
  @Override
  public void handleRequest(TrafficLight light) {
    System.out.println("Green light: GO!");
    light.setState(new YellowLightState()); // Transition to Yellow
  }

  @Override
  public String getStateName() {
    return "Green";
  }
}

// Concrete State: Yellow Light
class YellowLightState implements LightState {
  @Override
  public void handleRequest(TrafficLight light) {
    System.out.println("Yellow light: CAUTION!");
    light.setState(new RedLightState()); // Transition to Red
  }

  @Override
  public String getStateName() {
    return "Yellow";
  }
}

// Context
class TrafficLight {
  private LightState currentState;

  public TrafficLight() {
    // Initial state
    this.currentState = new RedLightState();
  }

  public void setState(LightState state) {
    this.currentState = state;
  }

  public void change() {
    System.out.print("Current state: " + currentState.getStateName() + " -> ");
    currentState.handleRequest(this);
  }
}

public class Main {
  public static void main(String[] args) {
    TrafficLight light = new TrafficLight();

    // Simulate light changes
    light.change(); // Red -> Green
    light.change(); // Green -> Yellow
    light.change(); // Yellow -> Red
    light.change(); // Red -> Green
  }
}