You can always static import Collections.sort. The main thing missing, then, is a way to simply refer to an existing method to perform the comparison. Is there syntax for this in the current release? (I believe there was in some of the earlier proposals.)
The definition of Comparator-interface includes only two methods, .compare and .equals. The documentations says that it is always safe to not override .equals, so we're left with just .compare. This effectively means that each comparator is effectively a function of two arguments that returns a boolean. Had functions been in Java in the first place, the whole Comparator interface would have been superfluous.