Is there any reason EnumMap and EnumSet are not Navigable

Question

Enum is Comparable which means you can have

NavigableSet modes = new TreeSet<>();
NavigableMap modeMap = ne         


        

Answer 1

Many "obvious" features are missing from the JDK and its various APIs. Why this particular feature was omitted / forgotten? We can only guess. But your question has been a RFE at Sun/Oracle for a long time:

• http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6278287
• http://www.java.net/node/644910

You could support those RFEs by commenting on them. Note, here's an authoritative answer by Joshua Bloch on the subject:

I vaguely recall considering it, but I can't recall whether we explicitly rejected it with good reason. We were running very low on time when I implemented EnumSet and EnumMap, and it's possible that time played a role in our decision

http://comments.gmane.org/gmane.comp.java.jsr.166-concurrency/2158

So even he had to guess :-)

Answer 2

My best guess is that navigability was not seen as a major use case for enum sets. There is nothing in the implementation that would prevent navigability. The rare use cases that combine the need for a set of enum members with navigability are covered by the TreeSet and TreeMap.

Answer 3

The post doesn't directly answers the question, neither attempts to, it merely conveys why Navigable was introduced

Post as I was requested to (and it's too long for a comment)

The short answer is that Navigable exists because we didn't have anything like upcoming "defenders" -- Sorted didn't describe all the common functionality, and there was no way to do so except to introduce a new interface. In practice, I'm sure "Sorted" is still used much more often than "Navigable" as a declaration type, because most people don't need the methods defined in Navigable but not Sorted. Plus "Navigable" is just not a very nice name :-)

-Doug