Concatinating two pdf files in java

How can I write java program to concatenate or merge two pdf files into one?
Can I do this using just java or need to use any third party software? If it is not possible, what is the free softwares available for this purpose?
Thanks in advance.

There is a nice set of libraries called iText that you can use to read and write PDFs. There is also a nice package called pdftk that you can use to manipulate PDFs.

Thanks Keith. I will go through those site and I know about them earlier.
I dont want to read or write pdfs.. I have all the pdfs and just I have to merge them into one.. Is it possible without them or will there be some functions in those api's to do this job?

Originally posted by Rizwan Mohammad:
Is it possible without them or will there be some functions in those api's to do this job?

No. A PDF contains hash like data about the whole file along with headers. You can't just concatenate them without reading them in first.

Originally posted by Rizwan Mohammad:
Thanks Keith. I will go through those site and I know about them earlier.
I dont want to read or write pdfs.. I have all the pdfs and just I have to merge them into one.. Is it possible without them or will there be some functions in those api's to do this job?

There are ways in both iText and pdftk. pdftk is probably easier to use for it since it is a command line program and you simply feed in the names of the .pdf files that you want to merge.

iText also comes with a ready-to-use example program that shows how to concatenate files.

Ulf & Keith, Thanks for your solutions. These helped me a lot.

Could any one know how read the pdf with font style, family and size for each and every word or line?.

Vijay,
your question has nothing to do with what was discussed above. Please don't post unrelated questions into existing topics; that's called "hijacking" and is frowned upon. Please start a new thread instead.