JAVA內建的觀察者模式樣本

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DisplayElement.java

public interface DisplayElement {public void display();}

CurrentConditionsDisplay.java

import java.util.Observer;import java.util.Observable;public class CurrentConditionsDisplay implements Observer, DisplayElement {    Observable observable;    private float temperature;    private float humidity;        public CurrentConditionsDisplay(Observable observable) {        this.observable = observable;        observable.addObserver(this);    }        public void update(Observable obs, Object arg) {        if (obs instanceof WeatherData) {            WeatherData weatherData = (WeatherData) obs;            this.temperature = weatherData.getTemperature();            this.humidity = weatherData.getHumidity();            display();        }            }        public void display () {        System.out.println("Current coditions: " + temperature                 + "F degress and " + humidity + "% humidity");    }    }

WeatherData.java

import java.util.Observable;public class WeatherData extends Observable {    private float temperature;    private float humidity;    private float pressure;        public WeatherData() {            }                public void measurementsChanged () {        setChanged();        notifyObservers();    }        public void setMeasurements(float temperature, float humidity, float pressure) {        this.temperature = temperature;        this.humidity = humidity;        this.pressure = pressure;        measurementsChanged();    }        public float getTemperature() {        return temperature;    }    public float getHumidity() {        return humidity;    }    public float getPressure() {        return pressure;    }    }

WeatherStation.java

public class WeatherStation {    public static void main(String[] args) {        // TODO Auto-generated method stub        WeatherData weatherData = new WeatherData();                CurrentConditionsDisplay currentDisplay = new CurrentConditionsDisplay(weatherData);        //StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData);        //ForecastDisplay forecastDisplay = new ForcecastDisplay(weatherData);                weatherData.setMeasurements(80, 65, 30.4f);        weatherData.setMeasurements(82, 70, 29.4f);        weatherData.setMeasurements(78, 90, 29.4f);            }}

 

JAVA內建的觀察者模式樣本