Suggest good Java IDE

I have recently started a Java course Online, I use the BlueJ IDE but i don’t feel 100% comfortable with it.
I wanted to know your opinions on a good beginner’s IDE from anyone involved in any form of java development. I Search on the Internet and others and they have recommended a few others, but if those are anything like BlueJ i’ll be inclined to say no thanks. I have heard good things about ItelliJ and NetBeans but everyone’s input will be much appreciated!

Source: XDA