Question

I am across situation where I will be changing key based on value in HashMap. My HashMap is:

HashMap<Key, Path>

Initially I am creating Keys for each directory Path and putting these entries in HashMap. When doing processing, I will take Path based on Key from HashMap and process them. In some cases I will be re-calculating Key for some Path and want to replace old Key with new Key for that Path. I want to keep unique Keys for unique Paths and update Entry in HashMap with either one. So I want to perform reverse of HashMap to update Key. What is best technique for this?

Thanks in Advance.

Answer 1

May be you are looking for Google Guava’s BiMap.

A bimap (or “bidirectional map”) is a map that preserves the
uniqueness of its values as well as that of its keys. This constraint
enables bimaps to support an “inverse view”, which is another bimap
containing the same entries as this bimap but with reversed keys and
values.