Hi Mie. Welcome to JavaRanch. In the Cattle Drive we suggest that the best IDE to use when you first learn Java is none. A text editor will help you better understand what is happening. And you don't need to worry about another thing to learn in addition to Java (how to use the IDE).
However, I think you really would get a better discussion about the pros and cons of various IDEs in the IDE forum, so I am going to move this thread there.
JavaBeginnersFaq "Yesterday is history, tomorrow is a mystery, and today is a gift; that's why they call it the present." Eleanor Roosevelt