Java is intended to be used by optimising JVMs. Java bytecode is rarely optimised -- that's left to the JIT. Using the Jazelle approach, where is the compiler optimisation step supposed to occur? Nowhere, of course! You'd be far better off with a decent conventional ARM JVM.
If you're on a system so lightweight that this isn't an option, well, you probably shouldn't have gone with Java. (Remember Java ME?)
[Not that I've ever actually worked with this stuff, mind.]