Minecraft wiki entry for Creating_Forge_mods, associated text: You can create a class to put your definitions in. Here we call it RegistryHandler, though some mods have separate classes for each type of object called ModItems, ModBlocks, etc; and in theory you could just add it to the main class. Having at least one class file (or, ideally, a package) to put registrations in without any non registration related code provides better organization for when you expand your mod.