Expert Java code reveiwer, we need your help!!

We had an consultant working for us a while back who wrote a MapReduce
framework for us. He claims that it works when he runs it on his
computer, but we have doubts about the code quality. Could you help us
point out issues in the code, where you find that the quality is less
than what you would require of a system before putting it into
production?

We are interested in issues related to all axis of software
development, including (but not limited to):

- Correctness
- Readability
- Maintainability
- Coding style
- Idiomatic use of the language
- Robustness
- Usability
- Extensibility
- Performance
- Formatting