If the end result can be achieved successfully in an acceptable timeframe on an 8051 using Java then it seems to me that there is no reason not to use it. As Jez points out there is often something of a kneejerk reaction from some contributors:

"The 8051 is the wrong processor for Java".

Ok, where does this belief come from? Is it based on their experience of using Java on the 8051? Probably not. So, why on earth do they think they are qualified to make such bold, definite statements?