The Indonesian Embassy in the Netherlands, which (as rickg523 posted) is one of the few sources of information you can trust to answer this question correctly, says in #41 on this page that you can apply for a 30-day visa on arrival and extend it once. You need a passport that is valid for at least six months after your arrival and a through or return ticket. The visa will cost USD35.

As for China, it depends on how long you plan to stay.