Commons math is a java library of lightweight, self-contained mathematics and statistics components.

commons math is made up of a small set of math/stat utilities addressing programming problems like the ones in the list below:
- computing means, variances and other summary statistics for a list of
numbers
- fitting a line to a set of data points using linear regression
- finding a smooth curve that passes through a collection of points
(interpolation)
- fitting a parametric model to a set of measurements using least-squares
methods
- solving equations involving real-valued functions (i.e. root-finding)
- solving systems of linear equations
- solving ordinary differential equations
- minimizing multi-dimensional functions
- generating random numbers with more restrictions (e.g distribution, range)
than what is possible using the jdk
- generating random samples and/or datasets that are "like" the data in an
input file
- performing statistical significance tests
- miscellaneous mathematical functions such as factorials, binomial
coefficients and "special functions" (e.g. gamma, beta functions)
this is a part of the apache commons project.