What are the differences between ConcurrentHashMap and Hashtable?

What are the differences between ConcurrentHashMap and Hashtable?

ConcurrentHashMap and Hashtable are both used for storing key-value pairs, but they have key differences. ConcurrentHashMap is designed for concurrent access, allowing multiple threads to read and write without locking the entire map, while Hashtable locks the entire map for each operation, which can lead to performance bottlenecks.

Which one is better for multi-threaded applications?

For multi-threaded applications, ConcurrentHashMap is generally better because it allows for higher concurrency and better performance under load. It uses a finer-grained locking mechanism, which means that multiple threads can access different segments of the map simultaneously.

Are there any scenarios where I should use Hashtable?

Hashtable is considered legacy and is rarely used in new applications. However, if you're working with older codebases that already use Hashtable, or if you need a synchronized map and don't require high concurrency, it might still be appropriate.

Can you give an example of how to use ConcurrentHashMap?

Sure! Here's a simple example:

ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
map.put("key1", 1);
map.put("key2", 2);

map.forEach((key, value) -> System.out.println(key + " : " + value));

This code initializes a ConcurrentHashMap, adds some key-value pairs, and prints them.