I still need to write tests for toArray, addAll, containsAll, retainsAll, removeAll, equals, hashcode

Wrote class, constructors and methods to pass tests completed. The following methods are completed and passing tests: size(), add(), isEmpty(), contains(), remove(), clear(), trimTrailingNull(), ShiftAllNullsToEnd()
Remaining methods to complete
both toArray(), containsAll(), addAll(), retainAll(), removeAll(), equals(), hashcode()

Remaining methods to complete
toArray() T[] toArray(T[] a)
removeAll(Collection<?> c)
equals(Object o)
int hashCode()
iterator---have no clue where to start with this one