These are all of my ProjectEuler solutions in Java so far. Some are incomplete, but I plan on adding a text file soon indicating if a particular solution is complete or in progress.
The Java source code can be found in the /src folder. The extra text files exist to provide context to some of the problems that required I read data from a provided text file.
Lastly, you can head over to projecteuler.net to view the actual problems themselves. Each problem increases in difficulty, so generally higher-numbered problems are harder to solve.