How to place labels on top of bars with some space in bar chart?

[daad.madhusudan]

I am working on a jasper report which generates a bar chart. My chart looks like this:

I am putting labels on top of bar using this line of code in my customizer class:

categoryPlot.getRenderer().setBasePositiveItemLabelPosition(new ItemLabelPosition(ItemLabelAnchor.OUTSIDE12, TextAnchor.BOTTOM_CENTER));

Now I want to increase the gap between top of bar and labels. How can I achieve this?