Utility to build a mold from an STL file

I am working with STL files for 3D printing. The STL files normally contain the hull of a shape with no thickness. Imagine the shapes to be similar to a cup that you drink from. With this as an input, the utility should do the following: 1. Calculate the volume of the shape. 2. Extend the top of the shape an additional 4 mm (just a plain extrusion). 3. Project an additional surface 0.8 mm outwards and close the shape at the top (just flat, nothing fancy). This is to create a mold that will have 2-part rubber poured into it. 4. Using a specific density (1.06 g/mm3) of liquid filled to the initial height (before the 4 mm extension), calculate and create supports for the mold such that it can withstand a 10 degree tipping without falling over. There should be 4 supports, projected from the calculated center of gravity, 8 mm x 0.8 mm, going up from the 'floor' at 55 degrees, with very small feet around the supports. 5. A small notch (running most of the length of one side) has to created on a specific side of the mold, which brings the thickness down to approximately 0.4 mm. 6. The output file must be a valid STL file, and must run as a command-line utility on linux. 7. Java is preferred, but if you have another suggestion, please mention it with your bid.