ArrayList and Vector

These are the key differences between ArrayList and Vector in Java:

Feature	ArrayList	Vector
Synchronization	Not synchronized, meaning it’s not thread-safe. If multiple threads access an ArrayList concurrently, external synchronization is required.	Synchronized, meaning it’s thread-safe. Methods in Vector are synchronized, which makes it slower compared to ArrayList in single-threaded scenarios.
Performance	Since it is not synchronized, it performs faster in non-threaded environments.	Due to synchronization, it has overhead and performs slower than ArrayList.
Growth Rate	Increases its size by 50% when it runs out of space.	Doubles its size when more capacity is needed.
Legacy Class	Part of the Java Collections Framework, introduced in Java 1.2.	Considered a legacy class, present since Java 1.0 but retrofitted to implement the List interface in Java 2.
Use Case	Suitable for general-purpose use where thread synchronization isn’t required.	Can be used in multi-threaded applications where a thread-safe implementation is necessary.

In most cases, ArrayList is preferred over Vector unless thread safety is specifically needed.