code: public void curveTo2 (final float x2, final float y2, final float x3, final float y3) throws IOException
    {
      if (inTextMode)
      {
        throw new IllegalStateException ("Error: curveTo2 is not allowed within a text block.");
      }
      writeOperand (x2);
      writeOperand (y2);
      writeOperand (x3);
      writeOperand (y3);
      writeOperator ((byte) 'v');
    }
docs: Append a cubic Bézier curve to the current path. The curve extends from the
  current point to the point (x3, y3), using the current point and (x2, y2)
  as the Bézier control points.
  
  @param x2
  x coordinate of the point 2
  @param y2
  y coordinate of the point 2
  @param x3
  x coordinate of the point 3
  @param y3
  y coordinate of the point 3
  @throws IllegalStateException
  If the method was called within a text block.
  @throws IOException
  If the content stream could not be written.