What is Java used for?
In the early days of Java it was assumed that the main use of Java would be as applets, small Java programs embedded in web pages. Applets offered the benefit of a fully fledged programming language allowing developers to embed just about any functionality. A combination of performance issues and lack of standardisation has hampered the widespread adoption of Applets in web pages, yet Java has had enormous take up as a programming languages in other areas.
One of the most significant (and not widely predicted) uses of Java is for Server Side web programming, or the creation of Web applications.
One of the most significant uses of Java is for Server Side Web programming, with Servlets, JSP and EJB technologies
This is very different from the original focus on applets as the resultant applications generally run exclusively on the server and thus (within reason) will run on any browser. The web browser (Netscape, IE, or Opera for example) sees a series of standard HTML forms and is unaware of what programming language is running on the server.
This is in significant contrast to Applets where the web browser needed to be configured up to run the right version of Java. Web applications are a huge area of growth with such Java technologies as Servlets, JSP and Enterprise Java Beans (EJB). Servlets and JSP are usually compared with Microsoft ASP and the Open Source PHP technology.
The database vendors have a huge need for portable software. Imagine you are running Oracle or Informix corporations and you need to develop for Windows XP plus heaven knows how many flavours of UNIX. This is probably why several of the Database Vendors (Oracle and Sybase to name two) have decided to embed Java virtual machines into the heart of their Database systems. Since the release of version 8.1 of Oracle a Java programmer has suddenly come a long way to being an Oracle programmer.