PMD error work-arounds:
Blocker - all delt with except 'VariableNamingConventions' in
MainController, the Proper names of planets and systems begin with upper
case letters
Critical - all delt with except Print statements
Important - all delt with except 'ShortClassName' apparently Ship.java
is too short a name to be acceptable

Word of warning, each time I run PMD, the number of errors changes up to
ten in either direction, even if I have made no changes to the code.