What is the reason for no ConcurrentHashSet against ConcurrentHashMap

Question

If we look at HashSet<E> implementation, everything is been managed under HashMap<E,Object>.

<E> is used as a key of HashMap.

And we know that HashMap is not thread safe. That is why we have ConcurrentHashMap in Java.

Based on this, I am confused that why we don't have a ConcurrentHashSet which should be based on the ConcurrentHashMap?

Answer 1

Hello,

There's no built in type for ConcurrentHashSet because you can always derive a set from a map. Since there are many types of maps, you use a method to produce a set from a given map (or map class).

As pointed the best way to obtain a concurrency-able HashSet is by means of Collections.synchronizedSet()

Set s = Collections.synchronizedSet(new HashSet(...));

Thank You!