Read the attached product brief on the Raspberry PI. Also look at some of the projects that have been built with the Raspberry Pi in the 2nd link. And yes, it can run Java.
Consider the following questions for your post.
1. Do you see anything that you would like to try or have the Raspberry PI do?
2. What does it mean to have this much computing power for $35 ? It was not too long ago that desktop PCs had these types of specs.
3. What other features or hardware to you think this needs to be usable?
If you think this is a toy, look at links below.