Collections - The Java Programming Language - page 861

Creates a new ArrayList whose initial contents are the con-
tents of coll . The capacity of the array is initially 110% of the
size of coll to allow for some growth without resizing. The or-
der is that returned by the collections iterator.
ArrayList also provides some methods to manage capacity:
public void trimToSize()
Sets the capacity to be exactly the current size of the list. If
the capacity is currently larger than the size, a new, smaller
underlying array will be allocated and the current values
copied in. You can thus reduce the amount of memory neces-
sary to hold the list, although at some cost.
public void ensureCapacity(int minCapacity)
Sets the capacity to minCapacity if the capacity is currently
smaller. You can use this if you are about to add a large
number of elements to the list, and so ensure the array will
be reallocated at most once (when ensureCapacity is invoked)
rather than possibly multiple times while the elements are ad-
ded.
21.6.2. LinkedList
ALinkedList is a doubly linked list whose performance characteristics are
virtually the reverse of ArrayList : Adding an element at the end is 0 (1),
but everything else is swapped. Adding or removing an element in the
middle is 0 (1) because it requires no copying, while getting the element
at a specific position i is 0 ( i ) since it requires starting at one end and
walking through the list to the i th element.
LinkedList provides two constructors and adds methods that are useful
and efficient for doubly linked lists: