Java - Difference between ArrayList and Vector in Java

http://javarevisited.blogspot.de/2011/09/difference-vector-vs-arraylist-in-java.html

Because sometimes I can't open this page without proper proxy configuration, so I have to copy some content here.

Similarities between ArrayList and Vector

1) Vector and ArrayList are index based and backed up by an array internally.

2) Both ArrayList and Vector maintains the insertion order of element. that's means you can assume that you will get the object in the order you have inserted if you iterate over ArrayList or Vector.

3) Both Iterator and ListIterator returned by ArrayList and Vector are fail-fast.

4) ArrayList and Vector also allows null and duplicates.

Difference between Vector and ArrayList

Differences are based upon properties like synchronization, thread safety, speed, performance , navigation and Iteration over List etc.

1) Synchronization and thread-safety

First and foremost difference between Vector and ArrayList is that Vector is synchronized and ArrayList is not. It means that all the method which structurally modifies Vector e.g. add () or remove () are synchronized which makes it thread-safe and allows it
to be used safely in a multi-threaded and concurrent environment. On the other hand ArrayList methods are not synchronized thus not suitable for use in multi-threaded environment.

2) Speed and Performance

ArrayList is faster than Vector. Since Vector is synchronized and thread-safe it pays price of synchronization which makes it little slow. On the other hand ArrayList is not synchronized and fast which makes it obvious choice in a single-threaded access environment.
You can also use ArrayList in a multi-threaded environment if multiple threads are only reading values from ArrayList or you can create read only ArrayList as well.

3) Capacity

Whenever Vector crossed the threshold specified, it increases itself by value specified in capacityIncrement field while you can increase size of ArrayList by calling ensureCapacity () method.

4) Enumeration and Iterator

Vector can return enumeration of items which it holds by calling elements () method. This enumeration is not fail-fast as opposed to Iterator and ListIterator returned by ArrayList.

5) Legacy

Another point worth to remember is Vector is one of those classes which comes with JDK 1.0 and initially not part of Collection framework but in later version it's been re-factored to implement List interface so that it could become part of collection framework.

After considering these points about both Vector and ArrayList , my conclusion is use ArrayList wherever possible and avoids use of Vector until you have no choice. Think for CopyOnWriteArrayList over Vector, if you have multiple
readers and few writers because it can provide thread-safety without impacting performance too much.