This recipe uses Cobertura (http://cobertura.sourceforge.net/) to find the code that is not covered by unit tests.
With consistent practice, writing unit tests will become as difficult as writing debugging information to
stdout. Most popular Java-specific IDE's have built-in support for running unit tests. Maven runs them as part of the test goal. If your code does not have regression tests, the code is more likely to break during refactoring. Measuring code coverage can be used to search for hotspots of non-tested code.
For more information, you can review http://onjava.com/onjava/2007/03/02/statement-branch-and-path-coverage-testing-in-java.html.
Install the Cobertura code coverage ...