HashMap vs ArrayList performance am I correct

Question

I currently believe that:

• When you need a structure from which you will be retrieving items randomly - use a HashMap
• When you will be ret

Answer 1

Don't forget it's also much faster to get to one specific item with a map (if you have the key) than it is from an array (unless you have an index, but a key will always get you the right value whereas having an index may not work if new elements are inserted or older ones removed).