From a chat session at vnunet.com on 7th September 1999:

'''RichardDrake''': Isn't pretty late to retrofit a decent collection class hierarchy in JDK1.2? Do you ever regret Java's typing or lack of HigherOrderFunction''''''s as you design stuff like collections? 

'''JamesGosling''': It is late to be doing collection classes. Java had some collection classes early on. The world would be better if we'd come up with collection classes earlier on, but on the priority list they didn't make it till a year ago. The problem with HigherOrderFunction''''''s is that it was and to some extent still is an open topic of research. While I like the idea of that, 6 or 7 years ago it wasn't obvious which solution would make sense. All the solutions had problems - usually performance. The situation has got somewhat better today. Some kind of HigherOrderFunction will probably arise, but it's going to take a while.