Design Pattern-Decorator

Definition: Dynamically attaches responsibility to an object. To extend functionality, decorators provide a more resilient alternative than inheritance.

UML diagram:

code example: Take my favorite ice cream as an example

/** Definition Ice Cream abstract class */

Public abstract class Ice {

Description

???? Public String desctription = "Unkonw";

???? Get Description

???? Public abstract String getdestription ();

???? Billing

???? public abstract double Cost ();

???? Print

???? public void print () {

???????? System.out.println (getdestription () + "/" + cost ());

????}

}

?

/** Milk Ice cream * *

public class Milkice extends ice{

???? Public Milkice () {

???????? TODO auto-generated Constructor stub

???????? Desctription = "milk";

????}

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???? public double cost () {

???????? TODO auto-generated Method Stub

???????? return 2.0d;

????}

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???? Public String getdestription () {

???????? TODO auto-generated Method Stub

???????? return desctription;

????}

}

?

/**

* define Ice cream decorator */

Public abstract class Icedecorator extends ice{

???? protected Ice mIce = null;

???? Public icedecorator (Ice ice) {

???????? TODO auto-generated Constructor stub

???????? MIce = ice;

????}

}

?

/** Strawberry Seasoning * *

public class Strawberrydecorator extends icedecorator{

???? Public strawberrydecorator (Ice ice) {

???????? Super (ICE);

???????? TODO auto-generated Constructor stub

????}

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???? Public String getdestription () {

???????? TODO auto-generated Method Stub

???????? return mice.getdestription () + "strawberry";

????}

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???? public double cost () {

???????? TODO auto-generated Method Stub

???????? return Mice.cost () + 0.5d;

????}

}

?

/** Chocolate Seasoning * *

public class Chocolatedecorator extends icedecorator{

???? Public chocolatedecorator (Ice ice) {

???????? Super (ICE);

???????? TODO auto-generated Constructor stub

????}

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???? Public String getdestription () {

???????? TODO auto-generated Method Stub

???????? return mice.getdestription () + "chocolate";

????}

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???? public double cost () {

???????? TODO auto-generated Method Stub

???????? return Mice.cost () + 0.8d;

????}

}

?

public class Main {

???? public static void Main (string[] args) {

???????? Ice Strawberry_milk = new Milkice ();// Definition Milk Strawberry ice cream

???????? Ice Chocolate_milk = new Milkice ();// define Milk chocolate ice cream

???????? Strawberry_milk = new Strawberrydecorator (strawberry_milk);// Add Strawberry decoration

???????? Chocolate_milk = new Chocolatedecorator (chocolate_milk);// Add chocolate decoration

???????? Strawberry_milk.getdestription ();

???????? Strawberry_milk.cost ();

???????? Chocolate_milk.getdestription ();

???????? Chocolate_milk.cost ();

????????

???????? Strawberry_milk.print ();

???????? Chocolate_milk.print ();

????}

}

Printing results:

milkstrawberry/2.5

milkchocolate/2.8

Design Pattern-Decorator