裝飾者模式：動態地將責任附加到物件上。想要擴充套件功能，裝飾者提供有別於繼承的另一種選擇。

裝飾者模式UML圖：

裝飾者模式具體例子：

public abstract class Beverage {
	String desription = "Unknown Beverage";
	
	public String getDescription(){
		return desription;
	}
	public abstract double cost();
	
}

public abstract class CondimentDecorator extends Beverage{
	public abstract String getDescription();

}
 

public class DarkRoast extends Beverage {
	
	public DarkRoast(){ 
		desription = "Dark Roast Coffee";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return 2.10;
	}

}

public class Espresso extends Beverage {
	
	public Espresso(){
		desription = "Espresso";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return 1.99;
	}

}
 

public class HouseBlend extends Beverage {
	
	public HouseBlend(){
		desription = "HouseBlend";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return .89;
	}

}

public class Mocha extends CondimentDecorator {
	Beverage beverage;
	
	public Mocha(Beverage beverage){
		this.beverage = beverage;
	}
	@Override
	public String getDescription() {
		// TODO Auto-generated method stub
		return beverage.getDescription()+", Mocha";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return .20 + beverage.cost();
	}

}
 

public class Soy extends CondimentDecorator {
	Beverage beverage;
	
	public Soy(Beverage beverage){
		this.beverage = beverage;
	}
	
	public int getSize(){
		return beverage.getSize();
	}
	@Override
	public String getDescription() {
		// TODO Auto-generated method stub
		return beverage.getDescription()+", Soy";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return  .10 + beverage.cost();
	}

}

使用場景：java.io類