Can you explain the internal implementation structure of ConcurrentHashSet?

ConcurrentHashSet in Java is usually implemented based on ConcurrentHashMap. Since there is no separate implementation of ConcurrentHashSet in the standard Java library, ConcurrentHashMap with a dummy value (e.g., Boolean.TRUE) for keys representing set elements is often used.

Inside, ConcurrentHashMap uses a segmented or more modern structure with multiple levels of locking (lock striping) to ensure high concurrency during access and modification. This allows multiple threads to read and write to different parts of the map simultaneously without locking the entire structure.

Example of creating a ConcurrentHashSet:

Set<String> concurrentHashSet = Collections.newSetFromMap(new ConcurrentHashMap<>());

Thus, ConcurrentHashSet inherits all the advantages of ConcurrentHashMap: thread safety, absence of global locks, and good performance under high contention.