Bhuvi, welcome to JavaRanch! If I may, I'd like to pass on some friendly advice based on your recent posts.
People volunteer their time here to answer questions, and we enjoy doing it to be sure. But like most people, we have busy lives that limit the amount of time we can devote. It will greatly increase your chances of getting answers if it's clear that you've done at least the bare minimum of work to answer your own question before posting. Better still if you've exhausted every resource you know.
As an example, I'm going to pretend I don't know the answer, and I'll time how long it takes to find an reasonable answer. Ready, set, go! . . . Done! Total time: two minutes. Granted, I knew what I was looking for, and I could quickly recognize a ballpark answer, but in this case it didn't even matter.
Entered [url=http://www.google.com/search?hl=en&q=java+design+patterns&btnG=Google+Search-"java design patterns"[/url] (no quotes) and hit enter.
First link was a Google search, skipped it.
Second link was a free PDF book -- looks good, but I didn't want to take the time to download it. I suggest you check it out though.
Third link was the actual PDF, skipped it.
Fourth link was a link to an index of the JavaWord "Java Design Patterns" articles, very promising indeed (check it out!), but I'm lazy so I skipped it. I was on the clock here!
Fifth link was one of those articles. The summary left no room for doubt -- I was home free!
Design patterns are proven techniques for implementing robust, malleable, reusable, and extensible object-oriented software.
Arguably not a very complete definition, but the article starts by extending that definition and continues to provide a few concrete (real-world) examples.
So my advice is that you make an effort to teach yourself before asking for others to teach you. Not only will you get more answers, but by learning how to find your own answers, you'll be able to get answers on your time instead of waiting for someone to respond. That in itself is very powerful and absolutely necessary in a job situation.
Best of luck! [ May 03, 2005: Message edited by: David Harkness ]