I am using JFreeChart in my java application.
Problem
I want to plot a XYAreaChart whose domain axis (x-axis)
You'll need to create your own SlidingXYDataset that implements XYDataset in a manner similar to how SlidingCategoryDataset implements CategoryDataset.
SlidingXYDataset
CategoryDataset
Addendum: As noted in a comment, a typical implementation can be found here.