Yeah I found the answer it was a very simple Logic,,,
and now
XYSeries SeperateY1 = new XYSeries("");
SeperateY1.add(3.5, 70);
SeperateY1.add(8,100);
SeperateY1.add(14,130);
XYMultipleSeriesDataset dataset = buildDataset(titles, x, values);
dataset.addSeries(SeperateY1);
Then for Y2 axis,,
i Created two more Lists and added
Y2.add(new double[]{80,90,100});
addXYSeries(dataset, new String[] { "" }, x2, Y2, 1);