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 access different segments concurrently without blocking each other.

In what scenarios should I use ConcurrentHashMap over HashMap?

You should use ConcurrentHashMap when you expect multiple threads to read and write to the map simultaneously. It's ideal for situations where thread safety is a concern, such as in a web application handling many requests.

Are there any performance trade-offs when using ConcurrentHashMap?

Yes, while ConcurrentHashMap offers better concurrency, it may have slightly higher overhead due to its locking mechanism. For single-threaded applications, HashMap is generally faster.