我怎样才能在java中拆分paint swing方法？

I'm developing a fair sized hospital simulation game in java. Right now, my pain method is starting to look a little big, and I need a way to split it up into different sections... I have an idea, but I'm not sure if this is the best way. It starts by painting the grass, then the hospital building, then any buildings, then people, then any building previews when building. The grass and hospital building will not change, so I only need to paint this once. The buildings themselves won't change very often, only when new ones are built.I'm developing a fair sized hospital simulation