Learn a little design pattern every day-decorator mode

Decorator Mode

English name

Decorator Pattern

definition

Dynamically attaches responsibility to objects, and to extend functionality, decorators provide a more resilient alternative than inheritance

Principles

1. Classes should be open to extensions, closed for modifications

2. This is the first model to conform to the "open close" principle

Understanding

1. To use decorators, first find the component that defines the decorator, defined as an abstract class, meaning an abstract interface.

2. Define an adorner component, also defined as an abstract class. An abstract component that is intended to be an adorner, but inherits the abstract interface defined earlier.

3. Implement specific components for an abstract interface.

4. Implement the specific decorator, each time the implementation is to pass the abstract interface object. This makes it convenient for the decorator to call the decorator's method.

5. The relationship between the component and the decorator is 1:n

Code

Component Abstraction Interface (decorator)

Public abstract class Beverage {
	String description = "Unknow beverage";
	
	Public String getdescription () {
		return description;
	}
	
	public abstract double Cost ();
}

Decorator Abstract Interface

Public abstract class Condimentdecorator extends beverage {public

	abstract String getdescription ();

Component-Specific implementation class

public class Darkroast extends beverage {public

	darkroast () {
		description = "Dark roast";
	}
	@Override public
	double Cost () {
		//TODO auto-generated method stub
		return 1.11;
	}

}

public class Decat extends beverage {

	/* (non-javadoc)
	 * @see com.sprd.pattern.decorator.beverage#cost ()
	 * /
	@Override public
	double Cost () {
		//TODO auto-generated method stub
		return 2.3;
	}

}

public class Espresso extends beverage {public
	Espresso () {
		Description = ' house Blend Coffee ';
	}

	@Override public
	double Cost () {
		return 1.99;
	}

}

public class Houseblend extends beverage {public
	houseblend () {
		Description = ' house Blend ';
	}

	@Override public
	double Cost () {
		//TODO auto-generated method Stub
		return.

Decorator Concrete Implementation

public class Mocha extends Condimentdecorator {
	beverage beverage;

	Public Mocha (Beverage beverage) {
		this.beverage = beverage;
	}

	@Override public
	String getdescription () {
		return beverage.getdescription () + ", Mocha";
	}

	
	@Override public
	double Cost () {
		return 0.2 + beverage.cost ();
	}

}

public class Soy extends Condimentdecorator {
	beverage beverage;
	Public Soy (Beverage beverage) {
		this.beverage = beverage;
	}

	@Override public
	String getdescription () {
		return beverage.getdescription () + ", Soy";
	}

	@Override public
	double Cost () {
		//TODO auto-generated method Stub
		return. 3 + beverage.cost ();
	}

}

public class Whip extends Condimentdecorator {
	beverage beverage;

	Public Whip (Beverage beverage) {
		this.beverage = beverage;
	}

	@Override public
	String getdescription () {
		return beverage.getdescription () + ", Whip";
	}

	@Override public
	double Cost () {
		return. 2 + beverage.cost ();
	}

}

Test program

public class Starbuzzcoffee {public

	static void Main (string[] args) {
		//dot a cup of espresso, nothing added
		beverage Espresso = NE W Espresso ();
		System.out.println (String.Format ("%s &%s", Espresso.getdescription (), Espresso.cost ()));
		Order a cup of deep roasted coffee
		beverage darkroast = new Darkroast ();
		Gamoca
		darkroast = new Mocha (darkroast);
		Double Mocha
		darkroast = new Mocha (darkroast);
		Add milk bubble
		darkroast = new Whip (darkroast);
		
		System.out.println (String.Format ("%s &%s", Darkroast.getdescription (), Darkroast.cost ()));
		
		Beverage houseblend = new Houseblend ();
		Add soy milk
		houseblend = new Soy (houseblend);
		Gamoca
		houseblend = new Mocha (houseblend);
		Add milk bubble
		houseblend = new Whip (houseblend);
		System.out.println (String.Format ("%s &%.2f", Houseblend.getdescription (), Houseblend.cost ()));
	}

}

Output results

House Blend Coffee & 1.99
Dark Roast, Mocha, mocha,whip & 1.71 House
Blend,soy, Mocha,whip & 1.59