How to use

setGradientPaintTransformer

method

in

org.jfree.chart.renderer.category.WaterfallBarRenderer

this.positiveBarPaint = positiveBarPaint;
this.negativeBarPaint = negativeBarPaint;
setGradientPaintTransformer(new StandardGradientPaintTransformer(
    GradientPaintTransformType.CENTER_VERTICAL));
setMinimumBarLength(1.0);

/**
 * Constructs a new waterfall renderer.
 *
 * @param firstBarPaint  the color of the first bar ({@code null} not
 *                       permitted).
 * @param positiveBarPaint  the color for bars with positive values
 *                          ({@code null} not permitted).
 * @param negativeBarPaint  the color for bars with negative values
 *                          ({@code null} not permitted).
 * @param lastBarPaint  the color of the last bar ({@code null} not
 *                      permitted).
 */
public WaterfallBarRenderer(Paint firstBarPaint, Paint positiveBarPaint,
    Paint negativeBarPaint, Paint lastBarPaint) {
  super();
  Args.nullNotPermitted(firstBarPaint, "firstBarPaint");
  Args.nullNotPermitted(positiveBarPaint, "positiveBarPaint");
  Args.nullNotPermitted(negativeBarPaint, "negativeBarPaint");
  Args.nullNotPermitted(lastBarPaint, "lastBarPaint");
  this.firstBarPaint = firstBarPaint;
  this.lastBarPaint = lastBarPaint;
  this.positiveBarPaint = positiveBarPaint;
  this.negativeBarPaint = negativeBarPaint;
  setGradientPaintTransformer(new StandardGradientPaintTransformer(
      GradientPaintTransformType.CENTER_VERTICAL));
  setMinimumBarLength(1.0);
}

GradientPaintTransformer gradientPaintTransformer = categoryRenderer.getGradientPaintTransformer();
if (gradientPaintTransformer != null) {
  renderer.setGradientPaintTransformer(gradientPaintTransformer);