Java Threading writing and reading at the same value?

Question

I have thread A and Thread B , what would happen if A reads an int value in A(itself) to check a condtion , while B is writing to the same value at the same time would an error occur ? or just desynchronization ?

Writes to int are atomic. In fact, in practice, writes to long are atomic too - but not guaranteed to be. So the write is atomic, but not visible. — Boris the Spider
– Boris the Spider, Commented Sep 13, 2014 at 17:14
What @BoristheSpider means by "atomic": When threads access an "atomic" variable with no synchronization, every read is guaranteed to get either the initial value, or a value that was stored by some other thread. When unsynchronized threads access something (usually an object) that is not atomic, there is no such guarantee: Thread A could see a "value" that is a mix of bits that were written by two or more different threads — Solomon Slow
– Solomon Slow, Commented Sep 15, 2014 at 0:59

Amir Afghani · Accepted Answer · 2014-09-16 03:29:18Z

1

What you've described is called a race condition. Each run of your program will have a different value stored in Thread A's memory where the result of the read is stored, all depending on the order of operations executed.

edited Sep 16, 2014 at 3:29

answered Sep 13, 2014 at 17:14

Amir Afghani

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Lucas · Accepted Answer · 2014-09-13 17:13:07Z

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No error, just unpredictable results. For that kind of operation use AtomicInteger or implement locking mechanism.

answered Sep 13, 2014 at 17:13

Lucas

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