I just installed Java SDK again as I know it but never use it so I plan to do some Java and XML stuff, but I learned it from books that I bought and read from my local library.
i know it, well, some. There are text books, but ya, there aint now way you could make runescape without some serious learning. Its the most beastly java program i know of.
I am not trying to discourage goals, but if you spend about 5 years doing Java to get up to a master level Java will either be no more, or newer versions. You also need great graphics skills for Runescape with vectors for resizing and it becomes quite difficult when you look at it.
I would aim for something like Utopia as it is much easier to make than any other as PHP is quite simple to learn.