Concurrent threads adding to ArrayList at same time - what happens?

Question

We have multiple threads calling add(obj) on an ArrayList.

My theory is that when add is called concurrently by two threads,

Answer 1

You could use instead of ArrayList(); :

Collections.synchronizedList( new ArrayList() );

or

new Vector();

synchronizedList as of me preferable because it's:

• faster on 50-100%
• can work with already existing ArrayList's