The user guide states that the JFontChooser class can be used in external applications.
However the scope of the class has not been explicitly set so is only available to classes defined in the same package and therefore not available to be used by external applications.
There are 2 options:
The class is made public and is available to be used by external applications.
The class remains protected and the user guide is updated to remove mention of the class.
Java 1.8 Windows 7 GeoTools 15/16