import java.util.*;
class GTM{
    public interface TemperatureObserver {
        void observed(double temperature);
        void noRead();
        boolean checkReading(double temp);
    }
    
    public List<TemperatureObserver> observers = new ArrayList<TemperatureObserver>();
    public void startMonitoring(final TemperatureSensor tr, final long pause){
        Thread monitorThread = new Thread(){
            public void run(){
                while(true){
                    try{ Thread.sleep(pause);}catch(InterruptedException ie){};
                    try{
                        double temp = tr.readTemperature(); 
                        for(TemperatureObserver to:observers)
                            if (to.checkReading(temp) ) to.observed( temp );
                    }catch(TemperatureSensor.SensorError re){
                        for(TemperatureObserver to:observers)
                            to.noRead();
                    }
                }
            }
        };
        monitorThread.start();
    }
    
    public static GTM getMeOne(){
        GTM gm = new GTM();
        TemperatureSensor ts = new TemperatureSensor();
        gm.startMonitoring(ts, 1000);
        return gm;
    }
}