Well, you certainly can use it with just an text editor. However, due to the maturity of the language and platform, the IDE support of Java is pretty much unsurpassed and you would certainly be quite a bit more productive if you used an IDE like IDEA or Eclipse.

In terms of complexity, it really depends on what you want to do. Using a powerful framework like Spring can entail some config (albeit much less than it used to). Also you would typically use a build tool like maven or gradle to manage dependencies, build artifacts, etc.. Especially maven can be a little arcane. But another major upside of the aforementioned maturity is that there are reams of docs and stackoverflow answers which will almost certainly contain solutions for any problems you might encounter.