Adding the Square

Now that we’ve got our color options using radio buttons on the left, it’s time to add the square that appears on the right. This is the visual part that actually responds to user input.

The square is going to be a Rectangle object from the JavaFX library. And remember, we want to:

• Set its initial color to red (to match the default radio button)

• Start it at 75% of the max size

• Place it in the window beside the radio buttons

Create the Rectangle

The assignment says the square should be 75% of a “maximum” size when the app starts. We’ll first define a constant for that maximum value. Put this at the top of your class:

private static final double MAX_SQUARE_SIZE = 200.0;

This means our full square size is 200 pixels. To get 75%, we just multiply: