Why Iterator<E> iterator() is put in Collection, AbstractCollection when already in Iterable [duplicate]

Question

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Why is there a method iterator() on java.util.Collection (4 answers)

Closed 8 years ago.

When Iterator iterator() is put in Iterable interface and this is extended by Collection interface and AbstractCollection interface, why this is again mentioned in Collection/AbstractCollection as no definition is given for this in abstract class.

Please help me to understand what I am missing in this from design perspective

Answer 1

The iterator() appears in Iterator and Collection as the Javadoc is different. In AbstractCollection it is different again, but doesn't appear to add much value.

Answer 2

Well Iterable is since 1.5 whereas Iterator and Collection are since 1.2. Not sure why AbstractCollection defines it again though, it's javadoc is slightly different though.