What would be an ideal environment for Java? What would be the ideal Operating System/Server, Server and Application Server, IDE, and what else does one need to set up a good, sound environment?
If you need a safe deployment environment you should probably go with Unix or linux systems. For easy (not always applicable) and unsafe development perhaps windos would suffice.
You IDE will pretty much (not totally though) depend on the underlying AppServer that you gonna be using. The most universal IDE that I've seen is the Eclipse at www.eclipse.org (yes, it's open source).
And if you pick Tomcat for your AppServer, again Eclipse could be the IDE of choice.