Generating a world with a custom BlockPopulator

public World createWorld()
{
    plugin.getServer().getPluginManager().registerEvents(this, plugin); // listen for events

    WorldCreator wc = new WorldCreator(Settings.killerWorldName).environment(Environment.NORMAL);
    World newWorld = wc.createWorld();

    HandlerList.unregisterAll(this); // stop listening for events

    return newWorld;
}

@EventHandler
public void onWorldInit(WorldInitEvent e)
{
    e.getWorld().getPopulators().add(new CustomPopulator());
}

public class CustomPopulator extends BlockPopulator
{
    public void populate(World world, Random random, Chunk chunk)
    {
        chunk.getBlock(8, 72, 8).setType(Material.GLOWSTONE);
    }
}