for v.s foreach 1. for loops on List are a bit more than 2 times cheaper than foreach loops on List. 2. Looping on Array is around 2 times cheaper than looping on List. 3. As a consequence, looping on Array using for is 5 times cheaper than looping on List using foreach. 4. LinkedList only allows foreach loops, as it would take quadratic time to loop a LinkedList through indices. 5. Looping overheads: for < foreach; Array ~ List < ArrayList < LinkedList
Everything stored in an ArrayList is an object. So be careful of the boxing/unboxing overhead.