java集合数据结构

Question

I need a data structure that does contains(element) quickly(preferably O(1)). also it allow me to iterate it in the order it comes in. HashSet satisfy the former, Vector satisfies the latter. does such thing exist in java.util?

Answer 1

LinkedHashSet ？

Answer 2

Look at the Linked* implementations. They preserve the insert order. In your case you need a LinkedHashSet .