Interface misunderstanding

[thejwal pavithran]

Vehicle.java :

package com.codebright;

public interface Vehicle {
	
	public void brake();
	public void speedUp();

}

landVehicle.java //excuse for not following naming convention for class name..

package com.codebright;

public interface landVehicle extends Vehicle
{
	public void gearChange(int num);
	
}

package com.codebright;

public interface waterVehicle extends Vehicle
{
	public void pedalChange(int num); 
}

package com.codebright;

public class LandWaterVehicle implements landVehicle,waterVehicle
{
	public void pedalChange(int num)
	{
		System.out.println("pedal Changed");
	}
	public void gearChange(int num)
	{
		System.out.println("gear changed");
	}
	public void brake()
	{
		System.out.println("brakes applied");
	}
	public void speedUp()
	{
		System.out.println("spped up");
	}
}

VehicleProgram.java

package com.codebright;

public class VehicleProgram 
{
	public static void main(String[] args)
	{
		Vehicle vehicle1 = new LandWaterVehicle();
		vehicle1.speedUp();
		vehicle1.brake();
		 vehicle1.pedalChange(3);  // the problem is here
		
		
		
	}
}

hey guys,

see the above code..in the VehicleProgram.java file,
the line vehicle1.pedalChange(3); is not compiling..but i dont get it..
i mean vehicle1 is a reference to an object of type LandWaterVehicle. so the method call should be legal right? i mean thats the whole point of run time displatch isnt it?

[I Wayan Saryada]

It is because the Vehicle interface doesn't have the pedalChange() method. The pedalChange() method is defined in the WaterVehicle interface. The LandWaterVehicle can be referenced by the Vehicle type because this class indirectly implements the Vehicle interface. But when you call the method from the Vehicle type it will not understand the call to pedanChange(). This interface only know how to brake() and speedUp().

[thejwal pavithran]

ok got it..remembering these things is slightly difficult for me..forming a logic seems easier.