What is the difference between a ConcurrentHashMap and a HashMap?

What is the difference between a ConcurrentHashMap and a HashMap?

A HashMap is not thread-safe, meaning multiple threads can cause data inconsistency. A ConcurrentHashMap, on the other hand, is designed for concurrent access, allowing multiple threads to read and write without locking the entire map.

Can you explain how ConcurrentHashMap achieves thread safety?

ConcurrentHashMap uses a technique called lock striping, which divides the map into segments. Each segment can be locked independently, allowing for better concurrency.

Are there any performance differences between the two?

Yes, ConcurrentHashMap generally performs better in multi-threaded environments because it allows concurrent reads and updates, while HashMap can lead to contention and performance degradation when accessed by multiple threads.

When should I use ConcurrentHashMap over HashMap?

Use ConcurrentHashMap when you expect multiple threads to access the map simultaneously. If you're working in a single-threaded context, HashMap is sufficient and may offer better performance.