Guide to the Java ArrayList

特点

• 存储的元素有序可重复
• ArrayList built atop an array, which is able to dynamically grow and shrink as you add/remove elements.

This ArrayListhas the following properties:

• Random access takes O(1) time（支持高效的随机元素访问）
• Adding element takes amortized constant time O(1)
• Inserting/Deleting takes O(n) time
• Searching takes O(n) time for unsorted array and O(log n) for a sorted one

时间复杂度函数图像