code: @SuppressWarnings("unchecked")
      static StyleConverter<?, Number[]> SizeConverter_SequenceConverter_getInstance() {
          try {
              if (mSizeConverter_SequenceConverter_getInstance == null) {
                  Class<?> c = Class.forName(isJava9orLater
                          ? "javafx.css.converter.SizeConverter$SequenceConverter"
                          : "com.sun.javafx.css.converters.SizeConverter$SequenceConverter");
                  mSizeConverter_SequenceConverter_getInstance = c.getMethod("getInstance");
              }
              return (StyleConverter<?, Number[]>) mSizeConverter_SequenceConverter_getInstance.invoke(null);
          } catch (ClassNotFoundException | NoSuchMethodException | SecurityException |
                  IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
              e.printStackTrace();
              throw new Error(e);
          }
      }
docs: Java 8:  com.sun.javafx.css.converters.SizeConverter.SequenceConverter.getInstance()
  Java 9+: javafx.css.converter.SizeConverter.SequenceConverter.getInstance()