I'd like to add one thing to this. UVa's judge support for Java is pretty bad (they're using old GNU Java compiler, instead of Sun's). Moreover, they're using ancient C/C++ compilers. While this doesn't affect much for C coders, for C++, you have to know the how much of STL you can use.
Should you want to practice using Java, I recommend using PKU (http://acm.pku.edu.cn) or ZJU (http://acm.zju.edu.cn) online judges. They have a good mixture of easy and hard problems. PKU even has more problems to solve than UVa.