In this example, Employee is a self-referential class because its next field has type Employee. This field is an example of a link field because it can store a reference to another object of its class ...
Yes it's linked list and has been at least back to 1.4 IIRC. But no matter what hashing method you use, you still need to check equals () in case of collisions (if not in hashCode, then in hashCode ...