It's an interesting idea but I've got a feeling that it would be handled, at least partly, server-side. So in order to do it you'd have to inject code, but more than likely some part of the process is run on their server, which would make it un-hack-able. Interesting concept though.
As for that picture of yours, I've got no idea what it is. Never seen it before. More than likely it's some other program you have installed or whatever. I don't think it has anything to do with PS2 though.
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And yes, you can program hacks in Java. The reason why it isn't really done though is because most games are coded in C/C++, so it's just harder generally to make a hack out of a different language. In addition, the way java works causes it to use massive amounts of memory when preforming a lot of tasks at once. If you've ever played Minecraft then you get the idea. It is possible to make hacks in Java, but it's just not practical.