How to convert Map to Map ? (option : using guava)

I have a Map the String key is nothing but numeric value like "123" etc. I'm getting numeric value because this values are coming from the UI in my JSF component. I don't want to change the contract of UI component.

Now I would like to create a Map based on the above Map, I saw some transform methods in the Maps class but all are focusing on the converting value and not key.

Is there any better way to convert Map to Map ?