This week's giveaway is in the Cloud/Virtualization forum. We're giving away four copies of Secure Financial Transactions with Ansible, Terraform, and OpenSCAP and have Lucian Maly on-line! See this thread for details.
I quickly looked at the code and there is one thing I noticed, lines 72 and 127 in AirDensityCalculator.java, in the method getDryAirDensity:
That is a really bad idea. It means the whole program stops immediately if that line is reached. Much better would be to throw an exception instead, for example:
Also, the design could be better. The code is getting messy with all those switch statements. You could use a design pattern such as the strategy pattern for the different calculations that are necessary for the different types of units.