Formatted code
Using Optionals rather than nulls
Added unit test
Updated to handle NPEs
Formatted
Added helper class for common-case HealthCheckService usage
Updated PowerFilter to use HealthCheckServiceHelper
Gave tests more descriptive names
Added NPE handling to more classes
Formatting
Refactored some code here
Updates to fix NPE exception
Updated test to handle Optionals
Updated another test to handle optionals
Fixed some code in PowerFilter that I broke when making changes
Added log messages
Capitalization of constants
Removed InputNullException from health check service register method, switch to static method name registering
Renamed a couple of SystemModelInterrogator methods to be self-descriptive
More constant variable naming convention stuff