// Parent class that represents a basic
// vehicle feature and function.
class Vehicle
  {
    int wheels = 4;
    public void engineStart()
     {
       System.out.println("Engine started. . .");
      }
    public void drive()
     {
       System.out.println("Driving on the pavement 
         on " +  wheels + " wheels.");
      } 
  }

// Subclass that uses the parent class' features 
// and adds a method unique to this kind of vehicle.
class Car extends Vehicle
 {
    public Car()
    {
      System.out.println("I'm a car:");
     }
    public void doorLock()
     {
       System.out.println("Locking all doors.");
      }
  }

// Subclass that hides the field of the parent  
// class with its own more appropriate data, and   
// adds a method unique to this vehicle.   
class Motorcycle extends Vehicle
  {
    // Hides the data of the parent class.
    int wheels = 2;
    public Motorcycle()
     {
       System.out.println("I'm a motorcycle:");
      }
    public void riding()
      {
        System.out.println("Riding on " + wheels +
                             " wheels.");
      }
    public void doingaWheelie()
     {
       System.out.println("Riding only on one wheel!");
      }
   }
// Subclass with additional data, a method 
// that overrides the parent drive method, 
// then later calls the parent's drive method 
// within a method for this subclass.
      
class Truck extends Vehicle
   {
    String storageBed1 = "long bed";
    String storageBed2 = "short bed";
      
    public Truck()
      {
        System.out.println("I'm a truck.");
       }
    // This method overrides the parent class
    // drive method, printing different text.     
    public void drive()
      {
        System.out.println("Use either 4-wheel 
          or 2-wheel drive."); 
      }
    
    public void showFeatures()
      {
        // Use of the super keyword here calls the 
        // drive method of the parent class. If you
        // omit super, then drive() from this 
        // subclass is called.
        super.drive();
        System.out.println("I have a " 
          + storageBed1 + " for storage.");
       }
   }
// Class to instantiate the object listed above and
// call the parent classes as well as the subclass
// methods.             
public class VehicleTest
 {
  
   public static void main(String[] args)
     {
       Car aCar = new Car();
       aCar.engineStart();
       aCar.drive();
       aCar.doorLock();
       
       Motorcycle aMotorcycle = new Motorcycle();
       aMotorcycle.engineStart();
       aMotorcycle.riding();
       aMotorcycle.doingaWheelie();
       
       Truck aTruck = new Truck();
       aTruck.engineStart();
       aTruck.drive();
       aTruck.showFeatures();
     }
  }