Hongxiang Qiu Hongxiang Qiu - 1 month ago 9
Java Question

TreeMap removing all keys greater than a certain key

In a project I need to remove all objects having key value greater than a certain key (key type is

Date
, if it matters).

As far as I know
TreeMap
implemented in Java is a red-black tree which is a binary search tree. So I should get
O(n)
when removing a subtree.

But I can't find any method to do this other than making a tail view and remove one by one, which takes
O(logn)
.

Any good ideas implementing this function? I believe treeMap is the correct dataStructure to use and should be able to do this.

thanks in advance

Answer

Quite simple. Instead of removing the entries one-by-one, use Map.clear() to remove the elements. In code:

map.tailMap(key).clear();