java if then error for fuzzy expert system

I am currently learning fuzzy expert systems and our tutor has supplied some Java code for creating a fuzzy system that determines mortgage eligibility. In the section that adds the rules to the system the code keeps coming up with an error. Can anyone suggest what might be wrong with this code that I can fix to make it work? I can't actually complete the lesson until this code starts working and the tutor is unavailable for two weeks.

if (marketValue is low) then (house is low)
ruleSet.addRule(marketValue, mvLow, house, houseLow);

if (location is bad) then (house is low)
ruleSet.addRule(location, locBad, house, houseLow);

Thanks for any help.