ConcurrentHashMap operations ordering guaranties

Asked Mar 10 '17 at 14:26

Active Mar 10 '17 at 14:53

Viewed 38 times

Lets imagine situation:

thread_1 put value to map (it continues from time_1 to time_4)

thread_2 want to read value from same segment(request was send at time_2)

thread_3 want to put value to same segment at time_3.

Is there guaranties about ordering of these operations?

P.S.
time_1 happens before time_2
time_2 happens before time_3
time_3 happens before time_4
[![enter image description here][1]][1]

edited Mar 10 '17 at 14:53

asked Mar 10 '17 at 14:26

gstackoverflow

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What do you mean by _ordering_ and _happens before_? What does the javadoc of the class say and what don't you understand about it? – Sotirios Delimanolis Mar 10 '17 at 14:41
@Sotirios Delimanolis who will win thread_2 or thread_3 ? – gstackoverflow Mar 10 '17 at 14:43
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What do you mean _win_? Win what? – Sotirios Delimanolis Mar 10 '17 at 14:43
@Sotirios Delimanolis which operation will be executed first? – gstackoverflow Mar 10 '17 at 14:44
Don't these sentences in the Javadoc explain it? "Retrieval operations (including get) generally do not block, so may overlap with update operations (including put and remove). Retrievals reflect the results of the most recently completed update operations holding upon their onset." – Andy Turner Mar 10 '17 at 14:45
You said at `time_2` and `time_3`, I don't know how you control that, but there's your answer. – Sotirios Delimanolis Mar 10 '17 at 14:45
@Sotirios Delimanolis I have added picture to the topic – gstackoverflow Mar 10 '17 at 14:47
http://stackoverflow.com/questions/26352707/what-happens-when-two-threads-trying-to-put-the-same-key-value-in-concurrent-has – Sotirios Delimanolis Mar 10 '17 at 14:51
@Sotirios Delimanolis, Why do you think that it is duplicate ? – gstackoverflow Mar 10 '17 at 14:57
Because that's the answer I would've given. – Sotirios Delimanolis Mar 10 '17 at 15:00
@Sotirios Delimanolis, I didn't find it – gstackoverflow Mar 10 '17 at 15:04
You're showing a `get` before a `put`. Obviously, the `get` won't retrieve a value that hasn't been `put` yet. Maybe I don't understand your confusion. _Retrievals reflect the results of the most recently completed update operations_ – Sotirios Delimanolis Mar 10 '17 at 15:22
@Sotirios Delimanolis oops, Do you want to say that read and write can ocсure in parallel? – gstackoverflow Mar 10 '17 at 15:22

ConcurrentHashMap operations ordering guaranties

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