Difference between Array and List in scala

Question

In what cases I should use Array(Buffer) and List(Buffer). Only one difference that I know is that arrays are nonvariant and lists are covariant. But what about performance

Answer 1

In addition to the answers posted already, here are some specifics.

While an Array[A] is literally a Java array, a List[A] is an immutable data structure that is either Nil (the empty list) or consists of a pair (A, List[A]).

Performance differences

                          Array  List
Access the ith element    θ(1)   θ(i)
Delete the ith element    θ(n)   θ(i)
Insert an element at i    θ(n)   θ(i)
Reverse                   θ(n)   θ(n)
Concatenate (length m,n)  θ(n+m) θ(n)
Count the elements        θ(1)   θ(n)

Memory differences

                          Array  List
Get the first i elements  θ(i)   θ(i)
Drop the first i elements θ(n-i) θ(1)
Insert an element at i    θ(n)   θ(i)
Reverse                   θ(n)   θ(n)
Concatenate (length m,n)  θ(n+m) θ(n)

So unless you need rapid random access, need to count elements, or for some reason you need destructive updates, a List is better than an Array.