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javamultithreadingconcurrencythread-safetyjava.util.concurrent

Does Set of ConcurrentHashMap is thread safe in foreach?

Is it safe to perform foreach, add, remove, size operations in different threads with the next set?

private final Set<MyObject>  myConcurrentHashSet = ConcurrentHashMap.newKeySet();

I.e. I don't need to get maximum accuracy in foreach or size operations but I need to be sure that there will not be any exceptions while I am doing foreach / add / remove / size operations.

I know that ConcurrentHashMap is thread safe, but I am confused about the thread safety of its Set.

Solution

  • Yes, the keySet view is thread safe, the newKeySet in java >=8 is equivalent to this java 7 form:

    for java <= 7

    ConcurrentHashMap c = ...;
Set threadSafeSet = c.keySet();

    for java >=8

    Set threadSafeSet =  ConcurrentHashMap.newKeySet();