Global stiffness matrix from element stiffness matrices for a thin rectangular plate (Kirchhoff plate)

I have the element stiffness matrix for a thin "kirchhoff" plate. The plate is 3 [m] x 5 [m] and is simply supported on all edges. It’s thickness is 0,2 [m]. On the plate there acts a constant load p = 5 [kN/m²]. For mu = 0,2 and E = 30000 [MPa] the displacement in the midpoint equals 0,168 [mm].

What’s the most efficient or quickest way and how to implement or code the assembly of finite elements of 0,5 [m] x 0,5 [m] for this plate and get the global stiffness matrix, the results as the nodal displacement vector and the nodal force vector?

Hints are appreciated. Thanks.

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EDIT: If somebody knows an open source free code or implementation for this very specific program written in Java, C++ or even in VBA, then this would be an answer for the question too!

EDIT: I found here a code that should work fine. How difficult is it to translate this code into another procedural programming language? How much pain is involved?