What is the difference between Hashtable and HashMap in Java?

What is the difference between Hashtable and HashMap in Java?

Hashtable and HashMap are both part of Java's collection framework, but they have some key differences. Hashtable is synchronized, meaning it's thread-safe, while HashMap is not. This makes HashMap generally faster in non-threaded applications. Additionally, HashMap allows null keys and values, whereas Hashtable does not.

Can you explain why synchronization is important?

Synchronization is important in multi-threaded environments to prevent concurrent access to shared resources, which can lead to data inconsistency or corruption. By synchronizing access to a Hashtable, you ensure that only one thread can modify it at a time.

Are there any performance differences I should be aware of?

Yes, HashMap is typically faster than Hashtable because it is not synchronized. If you don't need thread safety, HashMap is the better choice for performance.

When should I use Hashtable instead of HashMap?

You should use Hashtable when you need a thread-safe implementation and are working in a multi-threaded environment where multiple threads might access the same collection.