It seems that there are genres of problems for which much better performance and/or memory efficiency may be achieved by avoiding Java's object model and garbage collection. In my other comment in this thread, I mentioned my use case for in-memory database-y stuff. What else? Terracotta sells its "Big Memory" plug-in for EHCache which is basically a ByteBuffer-based in memory cache designed to reduce the number of objects visible to the garbage collector. Certainly manipulation of binary media formats qualifies (and the nearly-abandoned Sun/Oracle-provided libraries for doing so use such approaches, IIRC). What else?