Welcome to JavaRanch.
There's a historical reason why we have both Vector and ArrayList in the
Java library. Vector is a legacy collection class from Java 1.0. ArrayList was introduced in Java 1.2 with the
Collections Framework.
Vector was not removed from Java 1.2, because that would break many programs that people already had written before Java 1.2 came out.
Don't use Vector in any new code. If you really need a synchronized collection, then use Collections.synchronizedList(...):
See the API documentation for more information.
Note: This forum is about
servlets, but your question is not about servlets. Please choose an appropriate forum when you ask a question. I'm moving this question to a more appropriate forum.