Decorator Pattern

Decorator Pattern: attach additional responsibilities to an object dynamically. Decorators provide flexible alternative to sub classing for extending functionality.

Example

Account.java

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package com.decoratorpattern.example;   public abstract class Account {     String description;     public String getDescription() {   return description;  }    public void deposit() {   System.out.format("Amount was deposited into %s Successfully \n",getDescription());    }    public void withdraw() {   System.out.format("Amount  withdrawn from  %s Successfully \n",getDescription());    } }

NoFrillsAccount.java

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package com.decoratorpattern.example;   public class NoFrillsAccount extends Account{    public NoFrillsAccount(){   description = "NoFrills Account";  }   }

AccountDecorator.java

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package com.decoratorpattern.example;   public abstract class AccountDecorator extends Account {  public abstract void enableFeature(); }

InternetBanking.java

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package com.decoratorpattern.example;   public class InternetBanking extends AccountDecorator{     Account account;    public InternetBanking(Account account) {   this.account = account;  }  public String getDescription() {   enableFeature();   return account.getDescription() + " with Internet Banking" ;  }  @Override  public void enableFeature() {   System.out.format("Internet Banking Enabled for %s \n",account.getDescription());  } }

MobileBanking.java

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package com.decoratorpattern.example;   public class MobileBanking extends AccountDecorator{     Account account;    public MobileBanking(Account account) {   this.account = account;  }    public String getDescription() {   return account.getDescription() + " with Mobile Banking" ;  }     @Override  public void enableFeature() {   System.out.format("Mobile Banking Enabled for %s \n",account.getDescription());  }   }

AccountTestDrive.java

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package com.decoratorpattern.example;   public class AccountTestDrive {  public static void main(String[] args) {   Account noFrillsAccount = new NoFrillsAccount();   // NoFrills Account having basic features like deposit and withdraw   System.out.println(noFrillsAccount.getDescription());   // Now with the help of AccountDecorator, we have enabled Internet banking for the NoFrills Account   noFrillsAccount = new InternetBanking(noFrillsAccount);   System.out.println(noFrillsAccount.getDescription());    }   }

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