如何为paint方法准备可访问的数据

I have problem with script below - i dont know how to move to the next point. This part of script will show me coordinates from my XML (input.xml) file. But I would like to draw line (coordinates x0,y0,x1,y1) - obtained from my input I can see them if i return xList and yList, but i really dont know how to continue, how to prepare them to be accesssible for a paint method (graphics g).I have problem with script below - i dont know