how to make multiple worlds

I want to know how to make more than one world and how to change game rules for just one world I know of multiverse but I want to know how to do some of the stuff multiverse does I would also like to know how to delete worlds would I just delete the file or do I need to do more than that

 

with that link there is public WorldCreator(String name) I do not understand it a whole lot but would that just make a new world with a random seed also how would you unload the world

 

@Cat 700
https://hub.spigotmc.org/javadocs/s...it.html#unloadWorld-java.lang.String-boolean-
or
https://hub.spigotmc.org/javadocs/s...it.html#unloadWorld-org.bukkit.World-boolean-

calling createWorld on a WorldCreator will create the world with the settings as they are currently set in the WorldCreator. To set the seed, or any setting, call the corresponding method on a WorldCreator object. When all settings are set to your liking, call createWorld.

Seed is set with this for example. Scan through the documentation for the other setting methods.
https://jd.bukkit.org/org/bukkit/WorldCreator.html#seed(long)

 

how would I make a random seed or would not assigning a seed at all do that for me?

 

@Cat 700 I don't know anything about world creation but try not setting the seed. Otherwise you could set the seed to a random number using Random, Long.MAX_VALUE (and Long.MIN_VALUE if seeds can be negative).