private void step() {
int q = this.quantum;
int used;
Process proc;
// we MUST process the queues in reverse order for two reasons
// - so a process can't get promoted and re-calculated in another queue
// - so our wait times don't get messed up
for (int i = level.size() - 1; i >= 0; i--) {
// retrieve first item (does not remove!)
proc = level.get(i).peek();
// no process? good bye
if (proc == null) {
continue;
}
// how much of the quantum do we need to use?
used = q < proc.getBurstTime() ? q : proc.getBurstTime();
proc.changeBurstTime(-1 * used);
// finished and in the last fifo queue...
if (i == level.size() - 1) {
// and we're finished, lets remove this process
if (proc.getBurstTime() == 0) {
level.get(level.size() - 1).poll();
}
}
// if we aren't finished and are not in the last queue
// remove from current queue and move to next queue
else {
level.get(i).poll();
level.get(i + 1).offer(proc);
}
// finally, we add all the wait times to the other processes
// synchronized(level.get(i)) {
for (Process p : level.get(i)) {
if (p != proc) {
p.addWaitTime(used);
}
}
// }
}
}
