Java :: ArrayList VS Vector

ArrayList or Vector?

This is one of the famous questions that a Java beginner has in his mind. This is also a famous question asked in interviews. Following are the differences between ArrayList and Vector.

1. Vectors and Hashtable classes are available from the initial JDK 1.0. But, ArrayList and HashMap are added as a part of new Collections API since JDK 1.2.

2. Vectors and Hashtable are synchronized where as ArrayList and HashMap are unsynchronized.

When to use Vector? When to use ArrayList? 

1. ArrayList is faster when compared to Vector since ArrayList is unsynchronized. So, if the List will be modified by only one thread, use ArrayList. If the list is a local variable, you can always use ArrayList.
2. If the List will be accessed by multiple threads, always use Vector, otherwise you should take care of synchronization manually.

To visualize the problem with synchronization, try the following code.

There is a Producer class that adds 5000 elements to the List (ArrayList/Vector). Another class, Consumer class removes 5000 elements from the same list. There are around 10 producer threads and 10 consumer threads.

Reference:

http://skeletoncoder.blogspot.com/2006/09/java-tutorials-arraylist-or-vector.html