Why aren't variables in Java volatile by default?

Question

Possibly similar question:

Do you ever use the volatile keyword in Java?

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Today I was debugging my game; It had a very difficult threading problem that w

Answer 1

Volatiles are really only needed when you're trying to write low-level thread-safe, lock-free code. Most of your code probably shouldn't be either thread-safe or lock-free. In my experience, lock-free programming is only worth attempting after you've found that the simpler version which does do locking is incurring a significant performance hit due to the locking.

The more pleasant alternative is to use other building blocks in java.util.concurrent, some of which are lock-free but don't mess with your head quite as much as trying to do it all yourself at a low level.

Volatility has its own performance costs, and there's no reason why most code should incur those costs.