Decorator mode in Design Mode

Decorator mode definition: dynamically attaches a responsibility to an object. To expand the functionality, the decoration provides an alternative solution that is more flexible than continuing.

Simple definition: Wrap an object to provide new behavior.

The annotator mode can effectively deal with the explosion-like problem.

OO principles:

It is open to extensions and closed to modifications.

Take StarbuzzCoffee in the book as an example:

Beverage. java (Beverage abstract class)

package headfirst.decorator.starbuzz;public abstract class Beverage {String description = "Unknown Beverage";  public String getDescription() {return description;} public abstract double cost();}

CondimentDecorator. java (seasoning abstract class)

package headfirst.decorator.starbuzz;public abstract class CondimentDecorator extends Beverage {public abstract String getDescription();}

DarkRoast. java (beverage class)

package headfirst.decorator.starbuzz;public class DarkRoast extends Beverage {public DarkRoast() {description = "Dark Roast Coffee";} public double cost() {return .99;}}

Espresso. java

package headfirst.decorator.starbuzz;public class Espresso extends Beverage {  public Espresso() {description = "Espresso";}  public double cost() {return 1.99;}}

HouseBlend. java

package headfirst.decorator.starbuzz;public class HouseBlend extends Beverage {public HouseBlend() {description = "House Blend Coffee";} public double cost() {return .89;}}

Mocha. java (Specific spices class)

package headfirst.decorator.starbuzz;public class Mocha extends CondimentDecorator {Beverage beverage; public Mocha(Beverage beverage) {this.beverage = beverage;} public String getDescription() {return beverage.getDescription() + ", Mocha";} public double cost() {return .20 + beverage.cost();}}

Soy. java

package headfirst.decorator.starbuzz;public class Soy extends CondimentDecorator {Beverage beverage;public Soy(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Soy";}public double cost() {return .15 + beverage.cost();}}

Whip. java

package headfirst.decorator.starbuzz; public class Whip extends CondimentDecorator {Beverage beverage; public Whip(Beverage beverage) {this.beverage = beverage;} public String getDescription() {return beverage.getDescription() + ", Whip";} public double cost() {return .10 + beverage.cost();}}

Test class: StarbuzzCoffee. java

package headfirst.decorator.starbuzz;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);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());}}

Output:

Espresso $1.99Dark Roast Coffee, Mocha, Mocha, Whip $1.49House Blend Coffee, Soy, Mocha, Whip $1.34