I agree that Java suffers greatly from the absence of closures. However, I also fear that Java is designed in such a way, and has so much existing code, that it may be near impossible to add closures in a way that isn't confusing and doesn't break in unexpected ways.

Joshua Bloch thoroughly covers the relevant issues in these PowerPoint slides.

http://www.javac.info/bloch-closures-controversy.ppt

(I'm pretty sure the video is online too, if you Google a little more than I did.)