Short answer: supporting some kind of variance calculation was considered
and discussed by the Lambda expert group:


http://mail.openjdk.java.net/pipermail/lambda-libs-spec-experts/2013-March/001523.html

but since the well-known the formula you cite as-is fails catastrophically
for floating-point numbers and the numerical remedies for roundoff problems
are expensive enough that you don't want to do them all the time.

-Joe


On Mon, Mar 17, 2014 at 10:55 PM, clay <[email protected]> wrote:

> Why does jdk 8 java.util.DoubleSummaryStatistics not track variance or
> standard deviation?
>
> It provides mean, min, max, count, sum... But no variance? That's the
> other major statistic that can be calculated trivially by Var(X) = E[X^2] -
> (E[X])^2
>
> Java 8 hits final release today, right?
>
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