How to impliment the TableDecorator?

Question

How to impliment the TableDecorator in my project.Can anyone provide me the steps or code for that.

Refer to BalusC's excellent [GoF Design Patterns answer](http://stackoverflow.com/questions/1673841/examples-of-gof-design-patterns/2707195#2707195) for usage of the Decorator pattern in the Java Library — Sean Patrick Floyd, Apr 06 '11 at 09:22
Changing topic and content **after** receiving answers is not very nice - note, that my answer is valid for the *original* version of this question... — Andreas Dolk, Apr 06 '11 at 09:25
sorry for the inconvenience,previously topic is mistakenly written by — Anshul, Apr 06 '11 at 09:30

Andreas Dolk · Answer 1 · 2011-04-06T09:21:54.117

"Decorator" is not a class but a design pattern. You'll find a lot of implementations of this pattern in the java.io package (look at the streams, for example)

A prominent example, that explains a lot, is the BufferedInputStream. This class decorates any InputStream by adding some buffering.

Simple example:

 public interface GreetProvider { public String greet(); }

 public class HelloProvider implements GreetProvider { 
    public String greet() {
      return "Hello";
    }
 }

 public class ByeProvider implements GreetProvider { 
    public String greet() {
      return "Good Bye";
    }
 }

 public class SmilyDecorator implements GreetProvider {
    private GreetProvider provider;
    public SmilyDecorator(GreetProvider provider) {this.provider = provider;}

    public String greet() {
      return provider.greet() + " :-)";
    }
 }

 // somwhere in some method

 GreetProvider hello = new HelloProvider();
 GreetProvider bye = new ByeProvider();
 GreetProvider helloAndSmiley = new SmileyDecorator(hello);
 GreetProvider helloAndTwoSmileys = new SmileyDecorator(helloAndSmiley);

 System.out.printf("%s%n%s%n%s%n%s%n", 
       hello.greet(), bye.greet(),
       helloAndSmiley.greet(), helloAndTwoSmileys.greet());

Changing topic and content after receiving answers is not very nice - note, that my answer is valid for the original version of this question... — Andreas Dolk, Apr 06 '11 at 09:29

score 1 · Answer 2 · answered Apr 06 '11 at 09:18

Following classes uses decorator pattern:

All subclasses of java.io.InputStream, OutputStream, Reader and Writer have a constructor taking an instance of same type.
Almost all implementations of java.util.List, Set and Map have a constructor taking an instance of same type.
java.util.Collections, the checkedXXX(), synchronizedXXX() and unmodifiableXXX() methods.
javax.servlet.http.HttpServletRequestWrapper and HttpServletResponseWrapper

score 0 · Answer 3 · answered Apr 06 '11 at 09:28

OK, apparently we are talking about this TableDecorator class.

Although it is abstract, it has no abstract methods, so I guess the abstract modifier is just to stop you from instantiating the super class, use one of the subclasses instead:

Direct Known Subclasses: MultilevelTotalTableDecorator, TotalTableDecorator

(I don't think you are meant to implement your own TableDecorator class)

How to impliment the TableDecorator?

3 Answers3