Java is interpreted language, which is not good for big applications, especially games... And it consumes a lot of memory. To give you example, Mythruna with 128M clipping, and default shading quality (high) runs on my computer with max 20 fps when looking straight forward, it is worse result than CoD:MW3 (on lowest details)... After changing shading quality and reducing clipping distance, it runs good though. But it takes more memory and CPU than World of Warcraft...

Why Mythruna is being created with Java ? Why Java again for game like this ? It is a huge mistake, huge pain for players, it will have some performance issues, maybe huge issues.