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// Avant
public double getSpeed(Vehicule vehicule) {
  switch(vehicule.type) {
    case Camion:
      return getBaseSpeed() * loadFactor();
    break;

    case Avion:
      return getBaseSpeed() - windDragVector();
    break;

    case Moto:
    default:
      return getBaseSpeed();
    break;
  }
}

// Après
public abstract class Vehicule() {
  protected abstract double getSpeed();
}

public class Camion extends Vehicule {
  protected double getSpeed() {
     return getBaseSpeed() * loadFactor();
  }
}
public class Avion extends Vehicule { }
public class Voiture extends Vehicule { }