Re: Glitch in Java Collections (No descendingMap in LinkedHashMap)

From:

Daniel Pitts <newsgroup.nospam@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 05 Oct 2012 12:06:17 -0700

Message-ID:

<KcGbs.5480$w_2.2339@newsfe12.iad>

On 10/5/12 11:05 AM, Lew wrote:

Robert Klemme wrote:

Lew wrote:

Robert Klemme wrote:

Jan Burse wrote:

You get insertion order how?

First paragraph of JavaDoc:

Hash table and linked list implementation of the Map interface, with
predictable iteration order. This implementation differs from HashMap in
that it maintains a doubly-linked list running through all of its
entries. This linked list defines the iteration ordering, which is
normally the order in which keys were inserted into the map
(insertion-order). Note that insertion order is not affected if a key is
re-inserted into the map.

That says how you put the order, not how you get the order.

What are you talking about Lew?
The JavaDoc says specifically "with predictable iteration order.".

This indicates that the iteration order is the same as the order in
which items are "put", baring key collisions.

The interesting thing about this class is that it has no public methods that reveal
the order.

Why would they need to?

If the ordered state is not observable, what difference does it make?

The ordered state is observable through iteration. The OP was only
asking for reverse iterator, which isn't part of what he can get. I
wouldn't call that a glitch, just a feature request.

So what difference does the order make?

There are some use cases described in the class JavaDoc.

It doesn't explain how you reveal the order, only how you put it into another structure.

Iteration is how you reveal the order.