Coverage testing shows the lines of code that were not executed during the test. This can draw your attention to code that is not used and might therefore be a candidate for removal or refactoring.
To get coverage testing information for SimpleDebugging.java, you use the command:
java –Xrunjcov:type=M SimpleDebugging
As an experiment, try putting lines of code that will not be executed into SimpleDebugging.java (you’ll have to be somewhat clever about this since the compiler can detect unreachable lines of code).