I just saw a video showing how Notch (of Minecraft fame) is debugging and changing Minecraft while it is running. He pauses the game, changes something in the code and then unpauses the game where the change takes immediate effect without the need to restart the program.
How does this work? Which kind of technique is used to achieve this?
Best Answer
Java can do hot-swapping out of the box. If you use an IDE like Eclipse it will work for changing method-bodies. If you want to apply other code changes you might want to use a tool. JRebel is a product that supports more cases.
I don't want to do marketing for that product, but I personally do not know any other alternative. On the JRebel website there's a nice feature-comparison.
Hope that helps.