I agree with Zowee. Though often interchanged, the meaning is not quite the same for me. "I have lived in Japan for 4 years" gives the idea of 'residence' and location. If you said this to me, the first thing that comes to my mind is you living in some house or apartment at some location(s) for that period of time. I also think of your other experiences when you were in Japan, but this is somewhat 2nd in importance. "I have been in Japan for 4 years" in contrast gives less weight to this idea of 'residing' or location. Because you mention 4 years, I assume this, but with your statement I am thinking more about your general experiences in Japan.

I don’t think there is any difference in meaning between the two sentences, when you are talking about a period as long as 4 years. But if you were just visiting Japan for a week, you would say “I have been in Japan for a week” not “I have lived in Japan for a week.” “Lived” implies that the place is your permanent home. If you had just moved permanently to Japan and had only been there 1 week, you could say “I have lived in Japan for a week” because — even though you have only been there a short time — Japan is now your permanent home.

Yes! lived = stayed in a house, been = to be. You can use both interchagneably but the meaning is not the same. When you say 'lived' I think of you at home, when you say 'been' I think of experience in general...