What are the performance differences between HashMap and Hashtable?

What are the performance differences between HashMap and Hashtable?

HashMap is generally faster than Hashtable because it is unsynchronized, allowing for better performance in non-threaded applications.

Does that mean HashMap is not thread-safe?

Yes, that's correct. HashMap is not synchronized, so it is not thread-safe. If you need a thread-safe option, consider using ConcurrentHashMap.

What about memory usage? Is there a difference?

Yes, HashMap typically uses less memory than Hashtable because it does not have to maintain synchronization overhead.

Can you give me an example of when to use each?

Use HashMap for non-threaded applications for better performance, and use Hashtable or ConcurrentHashMap for multi-threaded environments.