Java Lock variable assignment before use. Why?

Question

In a lot of of the Java source, (for example LinkedBlockingDeque) I see things like this;

final ReentrantLock lock = new ReentrantLock();

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Answer 1

Whilst it shouldn't make any difference, it has been stated on mailing lists that there have been slight measured performance difference on actual JREs.

General advice would still be not to bother with the local. It's only there because performance is really, really crucial in specific code used by a lot of people.