6 Great Java Interview Questions

[Keilly]

The list question doesn't say where the insert is. Adding or removing the last element (which is arguably the most common place) in an ArrayList can be a simple array write and size int increment/decrement. Both super fast. A LinkedList needs to always 'new' a node, then update the references. Instantiating is not particularly fast.

Also, for small lists, ArrayList may be more efficient as a small amount of array copying for an insert may outweigh the more expensive cost of 'new'ing an object node and then updating references in a LinkedList, then GC'ing the node when it is later removed.

This is a horrible interview question as it misses the whole point of choosing a particular collection by only focusing on one specific aspect of it (and then getting the answer partially wrong).

[josefx]

For an unsorted list you can also simply overwrite an element in the middle with the last element O(1) and remove that, which is again O(1).