Question regarding Interface with instanceof operator

[ashwin bhawsar]

interface Vessel{}
class Boat implements Vessel{}

interface Toy{
	void toyMethod();
}

class SpeedBoat extends Boat implements Toy{ 
	public void toyMethod(){}
	}

public class Outer {
	public static void main(String[] args) {
		Boat b = new Boat();		
		System.out.println(b instanceof Toy);		
		b= new SpeedBoat();
		b.toyMethod(); // is illegal, b does't know anything about toyMethod() 
		System.out.println(b instanceof Toy);// then why this results in true, Why?
	}
}

[Nico Van Brandt]

instanceof checks for an 'IS-A' relationship. For that reason, because SpeedBoat is a Toy, it returns true.

[Karim Hamamouch]

I'd add that parent classes and interfaces are part of the inheritance tree of a class therefore the 'IS-A' principle is applied, as said previously'.

[Rob Spoor]

Even though at that time b is a SpeedBoat and therefore a Toy, the reference is used to determine which methods can be called, and the reference is one to Boat, not Toy or SpeedBoat. The compiler doesn't look at the actual value of the reference.

[ashwin bhawsar]

Thanks for all your replies