What are the performance differences between HashMap and ConcurrentHashMap?

What are the performance differences between HashMap and ConcurrentHashMap?

HashMap is not thread-safe, while ConcurrentHashMap is designed for concurrent access. This means that ConcurrentHashMap can handle multiple threads accessing it simultaneously without locking the entire map, which improves performance in multi-threaded environments.

Can you explain how the locking mechanism works in ConcurrentHashMap?

ConcurrentHashMap uses a technique called lock striping, where the map is divided into segments. Each segment can be locked independently, allowing multiple threads to read and write to different segments concurrently.

In what scenarios should I prefer ConcurrentHashMap over HashMap?

You should prefer ConcurrentHashMap in scenarios where multiple threads are accessing and modifying the map simultaneously, such as in a multi-threaded application where performance and data consistency are critical.

Are there any performance benchmarks available for these two data structures?

Yes, there are various benchmarks available that show ConcurrentHashMap performs better than HashMap under high contention scenarios, but HashMap can be faster in single-threaded situations.