(→Dois contextos) |
(→Dois contextos) |
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| Line 139: | Line 139: | ||
</source> | </source> | ||
| − | + | <source lang="java"> | |
| − | + | public class WeatherStationHeatIndex { | |
| − | + | public static void main(String[] args) { | |
| − | + | WeatherData weatherData = new WeatherData(); | |
| − | + | ||
| − | + | CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData); | |
| − | + | StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData); | |
| − | + | ForecastDisplay forecastDisplay = new ForecastDisplay(weatherData); | |
| − | + | HeatIndexDisplay heatIndexDisplay = new HeatIndexDisplay(weatherData); | |
| − | + | ||
| − | + | weatherData.setMeasurements(80, 65, 30.4f); | |
| − | + | weatherData.setMeasurements(82, 70, 29.2f); | |
| − | + | weatherData.setMeasurements(78, 90, 29.2f); | |
| − | + | } | |
| + | } | ||
| + | </source> | ||
[[category:Ensino]] | [[category:Ensino]] | ||
public interface Subject {
public void registerObserver(Observer o);
public void removeObserver(Observer o);
public void notifyObservers();
}
public interface Observer {
public void update(float temp, float humidity, float pressure);
}
Esta interface define o método básico para apresentação de dados.
public interface DisplayElement {
public void display();
}
As implementações da interface de apresentação, que implementam também a de observação, definem várias formas de exibição de dados.
public class CurrentConditionsDisplay implements Observer, DisplayElement {
private float _temperature;
private float _humidity;
private WeatherData _weatherData;
public CurrentConditionsDisplay(WeatherData weatherData) {
_weatherData = weatherData;
_weatherData.registerObserver(this);
}
public void update(float temperature, float humidity, float pressure) {
_temperature = temperature;
_humidity = humidity;
display();
}
public void display() {
System.out.println("Current conditions: " + _temperature + "F degrees and " + _humidity + "% humidity");
}
}
public class ForecastDisplay implements Observer, DisplayElement {
private float _currentPressure = 29.92f;
private float _lastPressure;
private WeatherData _weatherData;
public ForecastDisplay(WeatherData weatherData) {
_weatherData = weatherData;
_weatherData.registerObserver(this);
}
public void update(float temp, float humidity, float pressure) {
_lastPressure = _currentPressure;
_currentPressure = pressure;
display();
}
public void display() {
System.out.print("Forecast: ");
if (_currentPressure > _lastPressure) {
System.out.println("Improving weather on the way!");
} else if (_currentPressure == _lastPressure) {
System.out.println("More of the same");
} else if (_currentPressure < _lastPressure) {
System.out.println("Watch out for cooler, rainy weather");
}
}
}
Os dados de meteorologia correspondem ao objecto observado.
public class WeatherData implements Subject {
private ArrayList<Observer> _observers = new ArrayList<Observer>();
private float _temperature;
private float _humidity;
private float _pressure;
public WeatherData() { }
public void registerObserver(Observer o) { _observers.add(o); }
public void removeObserver(Observer o) {
int i = _observers.indexOf(o);
if (i >= 0) { _observers.remove(i); }
}
public void notifyObservers() {
for (Observer observer: _observers) {
observer.update(_temperature, _humidity, _pressure);
}
}
public void measurementsChanged() { notifyObservers(); }
public void setMeasurements(float temperature, float humidity, float pressure) {
_temperature = temperature;
_humidity = humidity;
_pressure = pressure;
measurementsChanged();
}
}
Os dois contextos de utilização correspondem a duas estações meteorológicas: em cada uma são utilizados observadores diferentes sobre os mesmos dados.
public class WeatherStation {
public static void main(String[] args) {
WeatherData weatherData = new WeatherData();
CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);
StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData);
ForecastDisplay forecastDisplay = new ForecastDisplay(weatherData);
weatherData.setMeasurements(80, 65, 30.4f);
weatherData.setMeasurements(82, 70, 29.2f);
weatherData.setMeasurements(78, 90, 29.2f);
}
}
public class WeatherStationHeatIndex {
public static void main(String[] args) {
WeatherData weatherData = new WeatherData();
CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);
StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData);
ForecastDisplay forecastDisplay = new ForecastDisplay(weatherData);
HeatIndexDisplay heatIndexDisplay = new HeatIndexDisplay(weatherData);
weatherData.setMeasurements(80, 65, 30.4f);
weatherData.setMeasurements(82, 70, 29.2f);
weatherData.setMeasurements(78, 90, 29.2f);
}
}