I have noticed this in the source code of a plugin, and thought to myself, hey, this looks great. So... I looked into it and couldn't get it to load up. I included the minecraft.jar and the minecraft_server.jar, though I didn't hold much hope for getting it from there considering they weren't API's, but I didn't find ANY reference to this anywhere. What JAR file do I need to download, and from where, to utilize the classes in there?