Detailed semantics of volatile regarding timeliness of visibility

Question

Consider a volatile int sharedVar. We know that the JLS gives us the following guarantees:

1. every action of a writing thread w precedi

Answer 1

I think the volatile in Java is expressed in terms of "if you see A you will also see B".

To be more explicit, Java promises that when you thread reads a volatile variable foo and sees value A, you have some guarantees as to what you will see when you read other variables later on the same thread. If the same thread that wrote A to foo also wrote B to bar (before writing A to foo), you're guaranteed to see at least B in bar.

Of course, if you never get to see A, you can't be guaranteed to see B either. And if you see B in bar, that says nothing about the visibility of A in foo. Also, the time that elapses between the thread writing A to foo and another thread seeing A in foo is not guaranteed.