If the interface doesn't declare an Exception, then you cannot declare any checked Exceptions in implementations. The intention of the method is to handle Exceptions without throwing anything else. The idea is that your implementation ought to be a refinement of the original method. So, every instance where the original method is feasible (ie runs without throwing an Exception) the implementation should be feasible (ie runs without Exceptions). You can fiddle it by throwing a RuntimeException or its subclasses. but that violates the spirit of refinement.
This is too difficult a subject for "beginning" so I shall move this
thread.