How to use Pair in Java and implementation

[cpu2007]

Hello everyone

I am trying to work on this problem but really failing understand it properly, I mean I understood the concept but having trouble knowing how to apply it.
Basically I need to read senstences using character reader and then find output the how many times each words has occured in the sentece or sentences

Here is the code:

public class ReadOne
{
    public Collection<Pair<String, Integer>> getAnswer(CharacterReader charac)  throws EOFException
   {

        throw new UnsupportedOperationException( "No implementation Found" );
    }
}

Now I have to implement the code in the class ReadOne but don't know how to do it.
I hope someone can provide some help
Thank you