Jama is not a complete solution for all of Java's multidimensional array problems. It is, rather, a basic linear algebra package with a focus on 2D arrays. Jama includes a Matrix class that provides a healthy set of methods for creating and manipulating 2D arrays. Jama also provides classes for a number of the more popular decompositions used in solving linear algebra problems. The program in Listing 1 is an example that shows off some of Jama's capabilities.
More examples are available in the downloadable package.
I solve the equations two ways. First, using Cramer's rule, which is defined in the sidebar. As you can see in Listing 1, I use the Jama constructors for building a Matrix from a 2D double array. I do this using one of Jama's submatrix methods. These submatrix operators are very powerful and have several variants.