Re: TreeMap question

From:

Lew <noone@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 22 Dec 2010 20:47:01 -0500

Message-ID:

<ieu9mf$pmt$1@news.albasani.net>

laredotornado wrote:

I'm using Java 1.6. I have a TreeMap that maps Integer to objects.
Given an integer that is given to be a key in this map, how can I
figure out what the key is immediately before the given one? Let me
know if this question doesn't make sense, - Dave

Patricia Shanahan wrote:

Use your TreeMap's lowerKey(K) method.

More generally, use the API documentation for Java 1.6. If you use an
older version of the documentation, you will miss out on some handy
java.util features.

Corollary point: This is a use case for a more specific type declaration than
'Map'.

The rule to use the most general applicable type does yield a very specific
type when that's called for.

A rigorous type-based approach would induce a declaration of 'NavigableMap' to
use 'lowerKey()'.

(Generics elided.)

Interesting that so much effort went into the collections framework for 6.
You are one of the few who really noticed. It's largely unheralded, being not
nearly so alluring as functors and fooferol.

This is Collections 3G - the third generation. They sure come in useful for
workaday programming. Maybe that's why they work on this area so hard.

--
Lew
Ceci n'est pas une pipe.