public void storeSignal(Signal s) throws NullPointerException {
public synchronized void storeSignal(Signal s) throws NullPointerException {
    public void storeSignal(Signal s) throws NullPointerException {        SignalMemory mem = (SignalMemory) get(Component.SIGNAL_MEMORY);        if (mem != null) {            mem.storeSignal(s);        } else {            throw new NullPointerException("Could not remember signal. The signal memory is null.");        }    }