java - Why Iterator<E> iterator() is put in Collection, AbstractCollection when already in Iterable -

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• why there method iterator() on java.util.collection 4 answers

when iterator iterator() put in iterable interface , extended collection interface , abstractcollection interface, why again mentioned in collection/abstractcollection no definition given in abstract class.

please me understand missing in design perspective

the iterator() appears in iterator , collection javadoc different. in abstractcollection different again, doesn't appear add value.