Re: Visitor pattern vs if-ladder

Wojtek <>
Thu, 23 Apr 2009 10:02:28 -0700
Philipp wrote :

I compared the speed of execution of an if-ladder with the visitor
pattern for counting different types of Vehicles.
If ladder:
public void count(Vehicle vehicle){
  if (vehicle instanceof Car) {
  } else if (vehicle instanceof Motorbike) {
  } else if (vehicle instanceof Bike) {

I set up an enum wich contains an instance of a class which does the

public interface BaseWorker
   public void doWork();

public class MotorBikeWorker implements BaseWorker

   public void doWork()
      .. do something

public enum CarWorker
  MOTOR_BIKE(new MotorBikeWorker()),
  BIKE(new BikeWorker());

  private BaseWorker worker;

  CarWorker( BaseWorker worker )
      this.worker = worker;

  public BaseWorker getWorker()
     return this.worker;

public abstract class Vehicle
   private CarWorker workerEnum;

   public Vehicle(CarWorker workerEnum)
      this.workerEnum = workerEnum;

   public final CarWorker getWorkerEnum()
      return this.workerEnum;

public class MotorBike extends Vehicle
   public MotorBike()

You then set up the class with the correct enum. To get work done you
simply call:


// um, this is from memory as my work machine is not connected to

Wojtek :-)

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