The world in question is currently in a ZIP inside my JAR file. Is it possible to extract it and teleport the player to it? I've been thinking about extracting it to the saves folder, but I have no idea how to get the path to the player's .minecraft folder in-code.

anyone?

Maybe you could generate a specific Dimension of the wanted world (or all) into the new World. How this could be done, no Idea. But you could have a look at different world-generator Mod sources. This helps me often when I'm modding

You can get the world saves folder quite easily:

 

DimensionManager.getCurrentSaveRootDirectory();

That gives you the current world's folder, so one level up is the "saves" directory, and one level above that is the main ".minecraft" directory. As for unzipping it, the standard java.util.zip package contains the classes/methods you need to extract files.

 

Unloading the current world and loading the new one, though... that's beyond my scope of knowledge.