Concurrent. ConcurrentHashMap class achieves thread-safety by dividing the map into segments, the lock is required not for the entire object but for one segment, i.e one thread requires a lock of one segment. In ConcurrenHashap the read operation doesn’t require any lock.

Is ConcurrentHashMap thread-safe?

Key points of ConcurrentHashMap: ConcurrentHashMap class is thread-safe i.e. multiple threads can operate on a single object without any complications. … The default concurrency-level of ConcurrentHashMap is 16.

Why is stack thread-safe?

Stack, which extends Vector, has every method synchronized. This means that interactions with individual methods are thread-safe. Queue is an interface. The safety of use across threads is up to the individual implementations.