Posted by: lrrp | March 15, 2006

How did I miss this? java.util.Collections

Well, they say you learn something new everyday. And given the size of the Java API, thats not too hard to believe.

After doing serious Java programming for at a least a few years, and having dabbled for a few years more (all the way back to the 1.0 days!), I’m pretty happy with my breadth of Java knowledge. Until a co-worker today mentioned using Collections.shuffle() to randomize a list.

“Pffffft”, says I, “Surely you jest”, says I. “No such thing.”

Well, there is. java.util.Collections (not Collection, note – theres an “s” on the end!). A nice, chunky class, full of juicy, static methods just waiting to save you from having to re-invent the wheel when it comes to operating on Collections. There’s the obvious stuff – shuffle() and sort() to randomize and sort, for instance. And small, but useful stuff – min() and max(), swap(). And some real useful stuff, like synchronizedList() (which returns a thread safe version of your list).

Many’s the time I’ve done my own “max()” routine. Each time, I trawled through the Collection interface looking for one and was mildly surprised it didn’t exist. And I never thought to look any further afield. I’m guessing that there may be one or two Java guys out there who are in the same boat (How many library classes are there now in Java?). Seeing as my co-worker doesn’t have his own blog…yet (come on H! Get your act together!), I’m doing this posting for the other people like me!

Of course, I’ve always got the excuse for my ignorance that its a relatively recent addition. I mean, its only been around since Java 1.2…..

Another good one along those lines is java.util.Arrays.



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