《Head First 设计模式》学习笔记——观察者模式 + 装饰者模式

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);
}

public interface DispalyElement {
	public void dispaly();
}

public class WeatherData implements Subject {
	private ArrayList observers;
	private float temperature;
	private float humidity;
	private float pressure;
	
	public WeatherData() {
		observers = new ArrayList();
	}
	
	public void registerObserver(Observer o) {
		observers.add(o);
	}
	
	public void removeObserver(Observer o) {
		int i = observers.indexOf(o);
		if (i >= 0) {
			observers.remove(i);
		}
	}
	
	//通知每一个观察者
	public void notifyObservers() {
		for (int i = 0; i < observers.size(); i++) {
			Observer observer = (Observer)observers.get(i);
			observer.update(temperature, humidity, pressure);
		}
	}
	
	public void measurementsChanged() {
		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;
	}
}

//测试代码
public class WeatherStation {
	public static void main(String[] args) {
		WeatherData weatherData = new WeatherData();
		
		CurrentConditionsDisplay currentDisplay =
		new CurrentConditionsDisplay(weatherData);
		
		weatherData.setMeasurements(80,65,30.4f);
	}
}

//抽象类
public abstract class Beverage {
	String description = "Unknown Beverage";
  
	public String getDescription() {
		return description;
	}
 
	public abstract double cost();
}

//CondimentDecorator必须能取代Beverage，所以将CondimentDecorator必须能取代Beverage，所以将扩展成Beverage类扩展成Beverage类
public abstract class CondimentDecorator extends Beverage {
	//所有调料装饰者必须重新实现getDescription()方法
	public abstract String getDescription();
}

//饮料代码扩展自Beverage
public class Espresso extends Beverage {
  
	public Espresso() {
		description = "Espresso";
	}
  
	public double cost() {
		return 1.99;
	}
}

//装饰者
public class Soy extends CondimentDecorator {
	Beverage beverage;//记录被装饰者

	public Soy(Beverage beverage) {
		this.beverage = beverage;
	}

	public String getDescription() {
		return beverage.getDescription() + ", Soy";
	}

	public double cost() {
		return .15 + beverage.cost();
	}
}

//测试代码
public class StarbuzzCoffee {
 
	public static void main(String args[]) {
		Beverage beverage = new Espresso();
		System.out.println(beverage.getDescription() 
				+ " $" + beverage.cost());
 
		Beverage beverage2 = new DarkRoast();
		beverage2 = new Mocha(beverage2);//层层装饰
		beverage2 = new Mocha(beverage2);
		beverage2 = new Whip(beverage2);
		System.out.println(beverage2.getDescription() 
				+ " $" + beverage2.cost());
 
		Beverage beverage3 = new HouseBlend();
		beverage3 = new Soy(beverage3);
		beverage3 = new Mocha(beverage3);
		beverage3 = new Whip(beverage3);
		System.out.println(beverage3.getDescription() 
				+ " $" + beverage3.cost());
	}
}