Yes, but if you really understand what it would take to make that work for real then you understand why it’s too hard to implement. It’s basically a similar reason as to why we only have a half-way implementation of generics.
Because what happens when you pass that to a method? (And remember, Java is not statically linked like C/C++.) What happens when you return it from a method? What happens when you have to support const casting to work with older libraries? (Oops… all benefits of const gone but with all of the new pain.)
Edit: and actually the const casting thing is probably a red herring because you just plain wouldn’t be able to work with old libraries most likely. The class formats would probably have to change in a very broken way (with respect to current formats).