Having read lots about volatile, atomic and visibility, one question remains. Following works across threads, "a" is visible all the time, when "b" is updated/read:
int a;
volatile int b;
a = 1; b = 1;
...
// different thread
if (b == 1) // do something with a, which is 1 now
Does the same hold true with atomic variables, which are separate objects, will the following work?
int a;
AtomicInteger b = new AtomicInteger();
a = 1; b.set(1);
...
// different thread
if (b.get() == 1) // a guaranteed to be 1 here all the time ???
If the answer is no, then it should work to extend the AtomicInteger class and include "a" within there, because AtomicInteger wraps a volatile.
A get() is equivalent to reading from a volatile variable, and a set() is equivalent to writing to it. We have a happens-before relationship here write -> read and therefore, "a guaranteed to be 1 here all the time". This of course is in the context of only these two threads executing.