==== Java interfaces ====

Similar to classes, but they does not contain any method implementations. An interface can extend other interfaces. 
Vehicle is a general interface, Car extends from a Vehicle it has more specific functions, similar to Motorcycle. 

Vehicle.java
  
  public interface Vehicle
  {
   public void hasWheels();
   public void hasEngine();
  }

Car.java
  
  public interface Car extends Vehicle
  {
   public void hasDoors();
   public void hasAirbags();
   public void hasRoof();
  }

Motorcycle.java
  
  public interface Motorcycle extends Vehicle
  {
   public void hasPedal();
   public void hasHandlebars();
   public void hasStand();
  }

Exercise 1.
  * Create a BMW class which implements Car interface.
  * Create a Skoda class implements car interface.

  public class TryItOut {
	public static void main(String[] args) {
                // creating a car array with 10 elements
		Car car[] = new Car[10];
		// create Skodas and BMWs (depending on the i-th index)
		for(int i=0; i < 10; i++) {
			if(i%2 == 0) {
				car[i] = new Skoda();
			} else {
				car[i] = new BMW();
			}
		}
		// call hasAirbags() method on each instance
		for(int i=0; i < 10; i++) {
			car[i].hasAirbags();
		}
	}
  }