Object resolution

[Jay Kay]

class A {}
class B extends A {}
class C extends B {}
class D extends C {}
The question is
Does (obj instanceof B) && ! (obj instanceof C)
correctly identifies whether the object referred to by obj was created by instantiating class B rather than classes A, C and D?
The answer is true. I agree that !(obj instanceof C) says that it does not belong to C or it's subclass D
But, how does it say that it does not belong to superclass A as
A is not mentioned in (obj instanceof B) && ! (obj instanceof C)
if the answer was
(obj instanceof B) && ! (obj instanceof C) && ! (obj instanceof A), then it is perfectly clear.
Any help is greatly appreciated.
-Jay

[Valentin Crettaz]

if you had created the object like this
A a = new A();
then the expression would evaluate to false, since A is not a subclass of B, but with the current expression, AS IS, the answer is correct since it correctly identifies an instance of class B and not A because obj is not an instance of C but is an instance of B!
Val