NOTE
Collections.synchronizedSet
Synchronized Set wrappers and the need for external synchronization during compound operations and iteration.
This is a historical learning note and may contain outdated or incomplete understanding.
Collections.synchronizedSet(set) wraps set operations with one mutex.
Iteration and compound multi-operation logic still require the documented external synchronization. Coarse synchronization can also become a contention point.
For concurrent set semantics, a ConcurrentHashMap-backed set or another specialized concurrent collection is often a better fit.