public class TestPlugin extends JavaPlugin implements Listener {
   private World world;

   @Override
   public void onEnable() {
      Bukkit.getPluginManager().registerEvents(this, this);
      world = Bukkit.createWorld(WorldCreator.name("test"));
   }

   @EventHandler
   public void onSpawnLocation(PlayerSpawnLocationEvent e) {
      Player player = e.getPlayer();
      System.out.println("spawn1: " + e.getSpawnLocation());
      if (e.getSpawnLocation().getWorld() == world) {
         e.setSpawnLocation(Bukkit.getWorld("world").getSpawnLocation());
      } else {
         e.setSpawnLocation(world.getSpawnLocation());
      }
      System.out.println("spawn2: " + e.getSpawnLocation());
   }
}