The problem with Java off-heap designs compared to C is that many Java language features become useless (e.g. instance variables, polymorphism, ...) and you lose the standard library as well as almost every single third party library out there.<p>In my view, sun.misc.Unsafe is extremely unproductive to work with. But I will say that it may be the right solution for adding a small very spcialized feature to a larger Java application.