Re: Best way to check if all elements in a List are unique

From:

Tom Anderson <twic@urchin.earth.li>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 3 Mar 2010 20:24:45 +0000

Message-ID:

<alpine.DEB.1.10.1003032021180.20166@urchin.earth.li>

On Tue, 2 Mar 2010, Lew wrote:

Mike Schilling wrote:

boolean areListElementsUnique(List<?> l)
{
return l.size() == new HashSet<Object>(l).size();
}

laredotornado wrote:

Winner! -

Lew wrote:

Don't forget to null-check the argument!

Tom Anderson wrote:

The method already does that - if it's null, you get a
NullPointerException.

Umm, the point of my comment was to *avoid* the NPE, duhh. Why cause trouble
for the method's client?

I'm hoping that you're being sarcastic. Or that i've misunderstood - i
read your comment as suggesting that the method should null-check the
incoming argument.

The right thing for this method to do if passed a null argument is to
throw an exception. There is no uncertainty about that. And it already
does that, so no check is necessary.

tom

--
But in the week its like Urbino under the wise rule of Count Federico,
only with a better football team and the nations most pleb-infested
Waitrose. And shops selling size 12 stilettos. -- Jelb, on Holloway