Question

Vector vs Arraylist (in non-multithreading environment) – in which requirements we will use Vector (rather than ArrayList)
One I know : if the size of the collection has to be increased dynamically and very frequently as vector size increases by 100% and ArrayList 50%

Answer 1

In a single thread environment never user Vector. Its methods are “synchronized” and this makes it slow, very slow against ArrayList.

So event if the ensureCapacity behavior is different, and Vector increase the size by 2, the cost of every single operation cannot be compared with the cost of the ArrayList operations, that are more fast.