Introduction to Threading in Java

Multithreaded (MT) programs are the current rage in computer science. Books upon books upon books have been written that describe the benefits of threading, the threading features inherent in various operating systems, and the various forms of threaded architectures.

So, what on earth are threads? How can you use them in your programs? Will threading continue to work in those applications that run native on operating systems that do not support threading? What does it mean to be MT-safe, and how do you design an MT-safe program?