007:When to use LinkedList over ArrayList?

题目：LinkedList与ArrayList区别，什么时候用他们

共同点：
1.实现List类

ArrayList：
1.内部通过数组实现，默认大小是20，每次默认增加空间为原来的1.5倍
2.可以在O(1)的时间内取出index位置的元素
3.插入，删除需要移动大量元素

LinkedList：
1.内部通过双链表实现，不需要对其扩容
2.查找指定index元素需要顺序遍历，时间复杂度O(n)
3.插入、删除不需要移动元素，只需要修改结点

LinkedList and ArrayList are two different implementations of the List interface. LinkedList implements it with a doubly-linked list. ArrayList implements it with a dynamically re-sizing array.

As with standard linked list and array operations, the various methods will have different algorithmic runtimes.

For LinkedList<E>

get(int index) is O(n/4) average
add(E element) is O(1)
add(int index, E element) is O(n/4) average
but O(1) when index = 0 <— main benefit of LinkedList
remove(int index) is O(n/4) average
Iterator.remove() is O(1) <— main benefit of LinkedList
ListIterator.add(E element) is O(1) <— main benefit of LinkedList
Note: O(n/4) is average, O(1) best case (e.g. index = 0), O(n/2) worst case (middle of list)

For ArrayList<E>

get(int index) is O(1) <— main benefit of ArrayList
add(E element) is O(1) amortized, but O(n) worst-case since the array must be resized and copied
add(int index, E element) is O(n/2) average
remove(int index) is O(n/2) average
Iterator.remove() is O(n/2) average
ListIterator.add(E element) is O(n/2) average
Note: O(n/2) is average, O(1) best case (end of list), O(n) worst case (start of list)

本专题来源stackoverflow 标签是java的投票数比较高的问题以及回答，我只对上面的回答根据自己的理解做下总结。