Java-Abstraction

/** Abstraction refers to vague definition or not very definitive nature of a class or a method.
* An abstract function should not have a body.
* If a class contains abstraction explicitly coded or inherited then the class must be stated as

* an abstract class using abstract keyword.
* A class with at least one abstract method should be declared abstract.
* We cannot create objects of an abstract class.
* Abstraction is used to enforce specifications and to hide complexity.
* A class inheriting an abstract class should define (should give body by overriding them) all

* the abstract functions in it or should be explicitly declared abstract.
**/



 

abstract class Vehicle {
 public abstract int numOfWheels();
 public abstract String steeringType();
 public abstract boolean hasGears();
 public abstract String fuelType();
 public abstract String getModel();
}

abstract class TwoWheelers extends Vehicle {
 public int numOfWheels() {
  return 2;
 }
 public String steeringType() {
  return "Handle Bar";
 }
}

abstract class FourWheelers extends Vehicle {
 public int numOfWheels() {
  return 4;
 }
 public String steeringType() {
  return "Steering Wheel";
 }
}

class Stallion extends TwoWheelers {
 public boolean hasGears() {
  return true;
 }
 public String fuelType() {
  return "Aviation Fuel";
 }
 public String getModel() {
  return "AK Automobiles - Stallion[NxtGen]";
 }
}

class Turtle extends TwoWheelers {
 public boolean hasGears() {
  return false;
 }
 public String fuelType() {
  return "Diesel";
 }
 public String getModel() {
  return "AK Automobiles - Turtle[No Worries]";
 }
}

class LoneRider extends FourWheelers {
 public boolean hasGears() {
  return true;
 }
 public String fuelType() {
  return "Petrol";
 }
 public String getModel() {
  return "AK Automobiles - LoneRider[Care For No One]";
 }
}

abstract class RentAVehicle {
 public static Vehicle getVehicle(String model) {
  Vehicle vehicle = null;

  if (model.equalsIgnoreCase("Stallion")) {
   vehicle = new Stallion();
  } else if(model.equalsIgnoreCase("Turtle")) {
   vehicle = new Turtle();
  } else if(model.equalsIgnoreCase("LoneRider")) {
   vehicle = new LoneRider();
  }

  return vehicle;
 }
}

class TestAbstraction {
 public static void main(String[] args) {
  try {
   Vehicle vehicle = RentAVehicle.getVehicle(args[0]);
   System.out.println("         Type: " + vehicle.numOfWheels() + " Wheeler");
   System.out.println("Steering Type: " + vehicle.steeringType());
   System.out.println("         Gear: " + (vehicle.hasGears() ? "Geared" : "Gearless"));
   System.out.println("    Fuel Type: " + vehicle.fuelType());
   System.out.println("        Model: " + vehicle.getModel());
  } catch (ArrayIndexOutOfBoundsException ex) {
   System.out.println("Error in usage !!!");
   System.out.println(getUsage());
  } catch (NullPointerException ex) {
   System.out.println("Sorry we do not have the specified model: " +
    args[0]);
  }
 }

 private static String getUsage() {
  return "Usage: java TestAbstraction <\"vehicle name\">";
 }
}