The method iterator () is declared in java.util.Collection and in java.lang.Iterable, its superinterface?

Question

Can someone explain to me why the Iterator<E> iterator(); method Iterator<E> iterator(); defined in java.util.Collection ? The collection is already expanding java.lang.Iterable ; this method is redundant. Is it for convenience?

Answer 1

The Collection interface was introduced in Java 1.2 using the collection API. Then the iterator method was used. However, the Iterable interface was not introduced prior to Java 1.5. The reason that Collection explicitly defines an iterator is because it precedes Iterable . The Collection idea of ​​returning an iterator precedes the idea of Iterable .