Effective Java. Clonable interface
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I read Effective Java book and don't understand one paragraph where explained Clonable interface. Can someone explain me this paragraph: 

> ...programmers assume that if they extend a class and invoke
> `super.clone` from the subclass, the returned object will be an instance
> of the subclass. The only way a superclass can provide this
> functionality is to return an object obtained by calling `super.clone`.
> If a clone method returns an object created by a constructor, it will
> have the wrong class.

Thanks.