Multi Thread Programming

Dear all,

I am new for java and multithread programming. I have two threads sharing a data, but one of this thread has to initiate third thread when some
condition failed, how it can be implemented in java? Anyone who are familiar with this,please give me piece pf code solving this issue.

Real scenario.
1. System Temperature [shared object by System and Temperature controller]
2. When temperature exceed some limit, Temperature controller should trigger the Advanced Temperature Controller.
Thanks