Data structures that can map a range of keys to a value

Question

I am trying to find a data structure that takes in a particular value from a range of values and map it to a key.

For example, I have the following conditions:

Answer 1

just have an List as a value in your Map.

Map> map = new HashMap>();

and also one Suggustion:

do not use Hashtable unless you want synchronized access.

EDIT:

Hashtable methods are synchronized, i.e., no two threads can access those methods at a single point of time. HashMap menthods are not Synchronized. If you use Hashtable there will be a performance hit. use HashMap for better performance.