Question: I have made an applet in vJ++ which I have to sign. Is there any tool to do it (both signing and cabbing)..?

Answer 1 was published yesterday.
Answer 2: Yes. Dubuild, which you can download from the Microsoft site as part of their Java SDK, can create signed CABs. There's good information on the whole process at:

http://www.suitable.com/docs/signing.html

By default, and for security reasons, Java applets are contained within a "sandbox." This means that the applets can't do anything which might be construed as threatening to the user's machine (e.g. reading, writing or deleting local files; putting up arbitrary message windows; communicating with arbitrary other machines; or querying various system parameters). Early browsers had no provisions for Java applets to reach outside of the sandbox. Recent browsers, however (Internet Explorer 4 on Windows, and Navigator 4 on all its platforms), have provisions to give "trusted" applets the ability to work outside the sandbox. For this power to be granted to one of your applets, the applet's code must be digitally signed with your unforgeable digital ID, and then the user must state that he trusts applets signed with your ID.

"However, you can also step outside the sandbox and write regular applications rather than applets, in which case you can access the other features of your OS. We’ve been writing regular applications all along in this book, but they’ve been console applications without any graphical components. Swing can be used to build GUI interfaces for regular applications.

You can generally answer the question of what an applet is able to do by looking at what it is supposed to do: extend the functionality of a Web page in a browser. Since, as a Net surfer, you never really know if a Web page is from a friendly place or not, you want any code that it runs to be safe. So the biggest restrictions you’ll notice are probably:"

More about Applets you can continue to read here in Thinking in Java book on our site

Java Code Examples for Applet you can find here