Performance: Iterating through a List in Java

Question

Is it slower to iterate through a list in Java like this:

for (int i=0;i

as opposed to:

Answer 1

No. It is faster (or should be faster) when the list also implements: RandomAccess (as ArrayList does and LinkedList doesn't).

However, you should always use the latter :

 for( Object o: list ) {
 }

and only switch to the former if your have substantial evidence that you're having a performance issue using it (for instance, you profile your application and as result you see as a point for improvement this section of code).

By not doing so, you risk not being able to switch your implementation in a later refactoring if your application requires it (because you would be tied to the for( int i = 0 ; i < list.size(); i++ ) idiom).