Java Developer is a broad title for anyone developing software using the Java programming language. What you do day-to-day depends a lot on the company you work for, there are good companies and bad companies. I am a Sr Software Engineer (basically a Sr Java Developer) and my week includes writing/testing/debugging java code, managing build/deployment scripts, managing development servers, writing code and usage documentation, team meetings, code reviews, internal education presentations, after-work LAN games, social lunches with other team members, and the occasional happy hour.
It's a job that you have to love to do well. The hours can be long, but if you are in a good company you can get compensation or flex time to offset (e.g. you work a 60-70 hour week and then take a take a long weekend or two later without subtracting from your vacation time)... yes, in both good and bad companies, you will work long hours. I generally work a 50-hour week during the light weeks... and up to 80 during crunch times, which thankfully dont happen all that often here.
The big thing is that you have to realize that going down either path will not immediately get you a job or the "big money". I have interviewed numerous candidates who had a CS degree with no experience that thought they should get a mid-level developer position and that they could "learn on the job"... you can and will learn on the job, starting from the bottom up. Experience is the most important key to getting a Java Developer position with a good company.