Is ConcurrentHashMap.putAll (...) "atomic?

Question

Is the ConcurrentHashMap.putAll (Map) method a putative atom?

I cannot find it in the documentation and it is not mentioned in the ConcurrentMap interface, so I think the answer is no. I ask him to be sure, because it would not make sense if this operation was not atomic, to be honest.

If it is not atomic, what would be the best way to support atomic inserts of several elements? Back to the good old sync?

Answer 1

It is not atomic, no. According to class documentation :

For aggregate operations such as putAll and clear , fetching at the same time may reflect the insertion or deletion of only certain entries.

To atomize it, you will need to use synchronized , yes. There is no non-blocking way to do this.

Answer 2

top document

For aggregate operations, such as putAll and clear , simultaneous searches may only reflect the insertion or deletion of certain records.

Answer 3

putAll() not atomic, but simply ensures that every single put() is atomic.

Answer 4

To atomize it, you have to use synchronized, yes

Not only that: you must place a synchronized block around each open card method, thereby reducing concurrency.