Arrays are random access, which means that access to any element
has the same cost.
a[i] is O(1).
Allocating a new array (not initializing the contents)
could be essentially O(1). However, since Java is type-safe,
the new array must be initialized for its contents type,
so creation of a new size n array costs O(n).
If the O(n) cost of array creation is amortized
over the n elements, the creation cost per
element is O(1).
Arrays are rigid: they cannot be expanded. One must either:
Get a new larger array and copy the old contents into it, O(n)
Make the array over-sized, wasting some space.
If an array is larger than main memory, the cost to access
an element can be much larger due to disk paging.