I was recently inspired to mess around with the Connect Four game I wrote in Java nearly a decade ago, and I ended up making three improvements to it: first, I fixed a deprecated function call in the code, which eliminates a warning message during compilation. Second, columns are now numbered 1-7 instead of 0-6, which is friendlier and makes it easier to enter your moves (since 0 is not to the left of 1 on the keyboard). Most significantly, though, there's a new ANSI color interface! The old plain-text UI is still available if ANSI color doesn't work for you.
My original intention was always to eventually learn how to do GUI programming in Java, and add a “GUI” class that would be a drop-in replacement for the existing “CLI” class. I still like that idea, but I'm no closer to being able to do it now than I was then. However, having all UI elements contained in their own class is interesting, and it's not something I would normally have done if I hadn't had this plan.
Anyway, you can download it from my Java page.