Actually, that's not accurate. The motivation for adding closures was to avoid adding those additional interfaces for the ParallelArray abstraction that goes o

Actually, that's not accurate. The motivation for adding closures was to avoid adding those additional interfaces for the ParallelArray abstraction that goes over fork/join. Fork/join has always been planned to go in for JDK 7. AFAIK, ParallelArray will not go into the new JDK 7 plan so the API stuff you mention is not an issue.