Question regarding Inrefaces:Please GUIDE.

Question

A question regarding INTERFACES.
'Each interface definition constitutes a new type.
As a result, a reference to any object instantiated from any class
that implements a given interface can be treated as the type of
the interface'.
So :
interface I{}
class A implements I{
}Now,class A is of type I.Right?
Now,if class A implements more than one interface,then what
is the actual type of A?
For example:
interface I{}
interface R{}
class B implements I,R{
}What is now B's type? I or R? or both?

Answer 1

>
The class (that implements the interface) actually
defines the behavior, and the interface just serves as
a contract for that behaviorYes.
- a view.Call it that if you want, but it being "a view" doesn't take away is-a-ness.
IMHO, the 'types' are the classes, which qualify for
the 'is a' relationshipAs yawmark points out, your use of "type" is not consistent with the JLS. Regardless of how you want to define type, the face it that it makes sense to say "A LinkedList is a List" and "A String is (a) Comparable" etc. Additionally, the way I've always seen the is-a relationship described, and the way that makes the most sense to me, is that "A is-a B" means "A can be used where B is expected." In this respect, superclasses and implemented interfaces are no different.
(which is what the words "extends" and "implements"
strongly suggest)"Foo extends Bar" in plain English doesn't suggest to me that Foo is a Bar, but quite clearly, in the context of Java's OO model, it means precisely that.
"Foo implements Bar" in plain English doesn't suggest much to me. Maybe that Foo provides the implementation specified in Bar, and therefore can be used where a Bar is required, which is exactly what implements means in Java and which, as far as I can tell, is the core of what the is-a relationship is supposed to be about in general OO.