How to create a .pdf file and write in it by Java

Suppose, I have given inputs in a window(like textfield, textarea, combobox etc.). Based on the information I need to write something in a .pdf file. How can I do it? Please reply me quickly.

There's and API named iText. It's free and open source and available for both Java and C#. Click here to go to the download page. Also, you may wanna check out the following links:
1. Tutorials
2. Documentation

Edit: There's another alternative thought. There are reporting tools that can do this and a (hell) lot of other stuff too. JasperReports is a reporting tool you may try. However, these are overkill and for simpler tasks, and i strongly suggest iText.

I think this link describe the fact betterhttp://www.vogella.de/articles/JavaPDF/article.html

even I have a book on iText, If you need, I can provide.