Why Java allows the use of obj with an interface

Question

I have this example, I can’t understand why java allows you to cast obj with an interface that does not implement it.

public interface Interface { public void whoIam(); } public class SuperClass { } public class SubClass extends SuperClass implements Interface { public void whoIam() { System.out.println("IM a SubClass"); } public static void main(String[] args) { SuperClass a = new SubClass(); Interface b = new SubClass(); Interface c = (Interface) new SuperClass(); c.whoIam(); } 

This line below should not compile, because SuperClass does not implement the interface:

  Interface c = (Interface) new SuperClass(); 

It will throw a "java.lang.ClassCastException:"

So, I think there is a reason the compiler resolves this line.

I would like to know when we can use obj with an interface when it does not implement it.

thanks