public void addTickGroup(Tick tock) {
LinkedList<Tick> newTicks = (LinkedList<Tick>) ticks.clone();
if (!newTicks.contains(tock)) {
newTicks.add(tock);
ticks = newTicks;
}
}
public void delTickGroup(Tick tock) {
LinkedList<Tick> newTicks = (LinkedList<Tick>) ticks.clone();
if (newTicks.remove(tock)) ticks = newTicks;
}