Question

I need to have a HashMap< Integer, String> which can serve fast operations for retrieving a list of all entries whose keys are in a certain integer range besides, getting values from map based on keys.

What Map implementation is suitable for these needs ?

Answer 1

Use a TreeMap, which implements NavigableMap supplying a subMap method returning a view of the map with only keys in your range. To get the values, of course you call values() on the result.

If you have an existing Map whose keys implement Comparable, you can construct a TreeMap from it by calling new TreeMap(existingMap), but it will likely be more efficient to create it as a TreeMap from the start.