How arraylist and vectors are different and in what case we should use array and in what case we should use vectors

ArrayList and Vector differs in synchronization, speed and increments when the maximum size has reached.

Explanation:

Synchronization - ArrayList is not synchronized where as Vector is synchronized. This means when multiple threads are accessing the ArrayList it must be synchronized externally where as Vector is synchronized by default. Vectors are not thread safe where as Array List are thread safe.

In case when the size of the array list reaches maximum it increments the size by 50% of the original size. Where as Vector size increments by 100% of the original size when the maximum it reaches the maximum length.

As Vector is synchronized it slow compared to Array List.