JavaFX supports gradients, which are smooth transitions between two or more colors. A gradient is defined by a set of stops, where each stop is a position along the gradient that has a specified color. JavaFX provides two types of gradients: linear gradients and radial gradients.

A linear gradient is a gradient that follows a straight line, while a radial gradient is a gradient that radiates out from a center point. You can use the LinearGradient and RadialGradient classes to define linear and radial gradients, respectively.

To define a linear gradient, you need to specify the start and end points of the gradient, as well as a set of stops. For example, the following code defines a linear gradient that starts at the top-left corner of a rectangle and ends at the bottom-right corner:

Rectangle rect = new Rectangle(100, 100, Color.WHITE);
rect.setFill(new LinearGradient(0, 0, 1, 1, true, CycleMethod.NO_CYCLE,
    new Stop(0, Color.RED),
    new Stop(0.5, Color.GREEN),
    new Stop(1, Color.BLUE)));

This code sets the fill of the rectangle to a linear gradient that starts with red at the top-left corner and transitions to green at the halfway point, then transitions to blue at the bottom-right corner.

To define a radial gradient, you need to specify the center point, radius, and a set of stops. For example, the following code defines a radial gradient that starts with white at the center of a circle and transitions to black at the edges:

Circle circle = new Circle(100, 100, 50);
circle.setFill(new RadialGradient(0, 0, 0.5, 0.5, 0.5, true, CycleMethod.NO_CYCLE,
    new Stop(0, Color.WHITE),
    new Stop(1, Color.BLACK)));

This code sets the fill of the circle to a radial gradient that starts with white at the center and transitions to black at the edges.