Stroking or Filling with a Gradient Color

 Color startColor = Color.red;
 Color endColor = Color.blue;
     
 // A non-cyclic gradient
 GradientPaint gradient = new GradientPaint(
   startX, startY, startColor, 
   endX, endY, endColor);
 g2d.setPaint(gradient);
 drawShape(g2d);
     
 // A cyclic gradient
 gradient = new GradientPaint(
   startX, startY, startColor, 
   endX, endY, endColor, true);
 g2d.setPaint(gradient);
 drawShape(g2d);