"interface" datatype variable??

Question

While working with other people's Code I found the following:
<code>
public interface iMyClass //the interface
public static string str = "";
public void setStr(String sStr);
</code>
and in the same package:
<code>
public class MyClass //the class
private iMyClass kuku; //a variable whose datatype is an interface
private void setStr(iMyClass); //at the interface the param is a string
// and here an interface!?
</code>
Is this possible?
I have learned the following:
KEYWORD: interface
A class description which is unimplemented, used only to describe methods and fields
which can later be provided by other (not necessarily subclass) classes.
<br>
<b>
1.How it is possible to declare a variable whose datatype is interface??
2.why the datatype changes at function?
3.why at the class declaration doen't appears the word "implement"
</b>
<br>
Thanks in advance for any help/links.
Bentzy

Answer 1

OK Dorceon, you are right.
But I found the following:
<code>
public class VClass implements iMyClass
private iMyClass kuku;
</code>
just to use the static members of the interface in the class functions this way:
<code>
this.kuku.str = "example"
</code>
why to declare the variable kuku?
can't I reach the interface variables this way?:
this.str = "example"
THANKS!!!!!!!