Sudoku with Java

I've got to tell you, to boast! There's a kind of logic game-puzzle, called Sudoku which is printed in the Independent - a 9x9 matrix of cells, some of them filled in with numbers from 1 to 9. You have to fill in the rest such that no rows or columns or subsidiary 3x3 blocks contain numbers the same. I have just written a recursive program, in Java, which gives a solution. I've been doing it for 3 days. Finally I got it working - at 3 a.m. last night!
I don't know why, but it does get to be an obsession. Programming requires precision and exactitude, a comma, a missed semi-colon and the thing wont work. The paradox is that I'm such a bodger. Why do I love forcing myself to adhere to such strict rules?