CountdownTimer.java

final GpioController gpio = GpioFactory.getInstance();
 List<Pin> segmentsPins = new ArrayList(Arrays.asList(RaspiPin.GPIO_25, 
                                                      RaspiPin.GPIO_02, 
                                                      RaspiPin.GPIO_24, 
                                                      RaspiPin.GPIO_23, 
                                                      RaspiPin.GPIO_22, 
                                                      RaspiPin.GPIO_21, 
                                                      RaspiPin.GPIO_00, 
                                                      RaspiPin.GPIO_07));
 List<GpioPinDigitalOutput> segments = new ArrayList<>();
 for (int i =0; i<segmentsPins.size(); i++){
 segments.add(gpio.provisionDigitalOutputPin(segmentsPins.get(i), PinState.LOW));
 }
 List<Pin> digitsPin = new ArrayList(Arrays.asList(RaspiPin.GPIO_26, 
                                                   RaspiPin.GPIO_05, 
                                                   RaspiPin.GPIO_03, 
                                                   RaspiPin.GPIO_01));
 List<GpioPinDigitalOutput> digits = new ArrayList<>();
 for (int i =0; i<digitsPin.size(); i++){
 digits.add(gpio.provisionDigitalOutputPin(digitsPin.get(i), PinState.LOW));
 }
 
Map<String, Integer[]> numbers =  new HashMap();
numbers.put("0", new Integer[]{1,1,1,1,1,1,0});
numbers.put("1", new Integer[]{0,1,1,0,0,0,0});
numbers.put("2", new Integer[]{1,1,0,1,1,0,1});
numbers.put("3", new Integer[]{1,1,1,1,0,0,1});
numbers.put("4", new Integer[]{0,1,1,0,0,1,1});
numbers.put("5", new Integer[]{1,0,1,1,0,1,1});
numbers.put("6", new Integer[]{1,0,1,1,1,1,1});
numbers.put("7", new Integer[]{1,1,1,0,0,0,0});
numbers.put("8", new Integer[]{1,1,1,1,1,1,1});
numbers.put("9", new Integer[]{1,1,1,1,0,1,1});

try{
    Calendar calendar = Calendar.getInstance();
    String time;
    while (true){
        calendar = Calendar.getInstance();
        time = new SimpleDateFormat("HHmm").format(calendar.getTime());
        for(int i=0; i<digits.size(); i++){
            for(int j=0; j<segments.size()-1; j++){
                segments.get(j).low();
                if(numbers.get(String.valueOf(time.charAt(i)))[j] == 1){
                    segments.get(j).high();
                }
                if(i==1){
                    segments.get(7).high();
                }else{
                    segments.get(7).low();
                }
            }
            digits.get(i).high();
        }
    }
}catch (Exception e){
    e.printStackTrace();
}

if(i==1 && seconds%2==0){
 segments.get(7).high();
}else{
 segments.get(7).low();
}