The netscape.javascript.JSObject.getWindow(Applet) method has been removed

The netscape.javascript.JSObject.getWindow(Applet) method was removed in Java SE 14. This method has not served any purpose since the removal of Java Plugins in Java SE 11, as the method will now only ever return null.

For more information on these changes, see Removal of netscape.javascript.JSObjectgetWindow Method.