How to use java code start a Start Events of BPM?

we need more document about BPM

for example:
we have a order;
after creat the order,we need start the Start Events in background;
then when the order over, we need edit state to over (the process end in background);
after edit order state,we can start next process in background.

Take a look here

PROCESS_CODE is the name you gave to BPM process.

THANKS´╝ü
and in the process,we have some service
the service might return some result,
and Determine whether to proceed to the next procedure based on the result.
how to do it