Implementation of the network simplex algorithm, see e.g. Vašek Chvátal: Linear Programming. Freeman, 1983.
This programming project was part of this class http://www.zib.de/groetschel/teaching/WS1415/VL-WS1415.htm.
My implementation was among the ones with top performance. Test data can be found at http://elib.zib.de/pub/mp-testdata/mincost/netg/index.html with a description of the data format here.
A very simple example instance is contained in the file simple_flow.
cd network-simplex
mkdir bin
javac src/*.java -d bin
cd bin
java nsimplex ../simple_flow