Definitely look into using Eclipse http://eclipse.org . I eschewed IDEs for a long time. I've tried all the commercial IDEs and disliked them. I was probably the only developer in my department who still used the console text editor vim exclusively. Finally Eclipse crept up on me; I felt like I had been technologically ignorant and asleep for the years that Eclipse existed and I had not been using it.
http://bluej.org/I think that's the most simple ide I've used. Currently, I have to use TextPad in school. It's quite annoying to see a school using TextPad and not even having paid for it. So every hour I get a little "buy me now" reminder. Cheap school. But TextPad is about as simple as notepad, but I wouldn't reccommend it for large projects.
BlueJ is the worst IDE out there. It doesn't even work properly. Sometimes it tells you that you have a syntax error when you don't. In order the fix that you have to click compile 900 times and it finally compiles without error. It also has trouble with comments and locks up at least once every use.
Netbeans - it has everything you will ever need...
I tried JCreator, which I like it for simplicity, had quick look on Eclipse, that is great with all additional plugins. I also tried NetBeans, which is great as being free IDE, however after spending last 8 months working with IntelliJ Idea I would'nt trade it (money well spent)