Java Unit Testing Completeness Indicator Tool?
I am talking about the real 'Test Completeness', not the traditional 'Code Coverage'，because Code Coverage is not very helpful when people start asking for more accurate estimations.
And by 'Test Completeness' I mean that (virtually) ALL possible usages of a function are covered, including Border conditions of the arguments, etc.
There is another Stackoverflow thread discussing this topic, but no java tool is mentioned in it.
Is there such as tool that can take a look at the current JUnit Tests and tell me approximately the percentage of completeness?
Have you tried Jacoco? Jacoco generates line and branch coverage (more info in the docs). I'm not really sure if that covers your "completeness" definition. Personally, I don't write many unit tests, I use the Java Agent to show lines/branches executed during functional automated tests (this feature is totally awesome). I hope it fits what you are looking for.
If not, I hope others add it to there test automation stack, it gives you hard numbers on what lines of code are being executed in your automated or manual tests.