I'm displaying the results of a clustering operation on a XYLineChart using JFreeChart. For now the plot I get is this one:

I need to change the x axis in order to get this display:

So basically I first need to get rid of the tick and numbers (this I already searched and found a way to manage how to do it). The problem for me is to add my own custom String values on the x axis AND to have these positionned at specific position. I already have an arraylist with the Strings and another one with the position values, no need to calculate them, i just want to know how to use them with the plot.
Thank you in advance and, as usual, please tell me if my explanation needs to be clarified.