What is the difference between ConcurrentHashMap and SynchronizedMap?

What is the difference between ConcurrentHashMap and SynchronizedMap?

ConcurrentHashMap is designed for concurrent access, allowing multiple threads to read and write without locking the entire map. In contrast, SynchronizedMap wraps a regular map and synchronizes all access, which can lead to performance bottlenecks.

When should I use ConcurrentHashMap over SynchronizedMap?

You should use ConcurrentHashMap when you expect high concurrency and need better performance. SynchronizedMap is suitable for lower concurrency scenarios where thread safety is required but performance is not a critical concern.

Are there any performance benchmarks comparing the two?

Yes, benchmarks typically show that ConcurrentHashMap performs significantly better under high contention due to its finer-grained locking mechanism compared to the global lock of SynchronizedMap.

Can you give an example of how to implement both in Java?

Sure! For ConcurrentHashMap, you can use: ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();. For SynchronizedMap, you can use: Map<String, Integer> map = Collections.synchronizedMap(new HashMap<>());.