Apache Commons Statistics: Descriptive

Apache Commons Statistics provides implementation of univariate statistics.

Example:

java.util.stream.Stream
import org.apache.commons.statistics.descriptive.Variance;

// Support a fixed size array
double[] values = {1, 1, 2, 3, 5, 8, 13, 21};

double v = Variance.of(values).getAsDouble();

// Support streams
double v2 = Stream.of("one", "two", "three", "four")
                  .mapToDouble(String::length)
                  .collect(Variance::create, Variance::accept, Variance::combine)
                  .getAsDouble();

Browse the Javadoc for more information.