Preemption of Java thread (WARNING: Experts only)

Question

Hi java experts,
I am thinking about a task scheduler. I would like to create my task scheduler a little bit like a CPU scheduler in such a way that it can support many scheduling algorithms.
So my task scheduler could be a pool of thread that keep one or many queue(s) of tasks. It seem reasonnable that Task objects implements Runnable but it's not necessary; instead, a Task could be like an event and the TaskScheduler could dispatch a thread to an EventHandler implementing Runnable that will process the task.
Some scheduling algorithms are easy to implements, like FCFS (First-Come, First-Served). But, others seem very hard to implements because algorithms use preemtion for time-sharing, like RR (Round-Robin).
Thus, is-it possible to preempt a java thread or simulate this behavior?
-Jean

Answer 1

Whatever scheduling algorithm you use
will depend on the underlying OS scheduling algorithm
and the restrictions imposed by Java's WORA nature.The JVM schedules threads using a preemptive, priority-based scheduling algorithm. So, if a thread with a higher priority than the thread currently running enters the Runnable state, the JVM preempts the currently running thread and executes the thread with the higher priority. With this in mind, I think that it could be possible to create a TaskScheluer with a preemtive behaviour, maybe by modifying dynamically the threads priority...