Evidence; that your code will work
Java has an incredible number of frameworks for… everything. There are dozens of web frameworks alone, several of which are official standards: Applets, Servlets, JSP/JSTL, JSF and now JavaFX. This doesn’t even include the OSS efforts. It’s the same story for persistence, version/source control, testing, etc.
As a language matures and gains market/mindshare these things happen. If you are opposed to innovation and choice, and all the warts that comes with, an application stack from Microsoft is something to consider. They usually have only 1 or 2 ways of doing things and are those usually supported w/tools and documentation.
