Looks like you have waited too long to see if something will happen in your career development towards Java. Did you try any certification during this time ? Or anything voluntary with Java development ? Anyway,now, finally you have a Java opportunity. Just try to understand what you will need to get that done. Take any trainings (outside of your office), or learn by yourself by putting some extra hours. See if you can do a sample prototype for your project first. Identify the areas which you have difficulty and see if you can get some help there. Through the other Java forums we have in Ranch and so many other resources in the net. Give it your best shot, whatever the outcome may.
These are just a few thoughts I have, others in the forum will have a lot more.