spigot coding how to send a message to player after commadn

1//After Command
2public boolean onCommand(CommandSender sender, Command cmd, String[] args, String tag) {
3	if(tag.equals("test")) {
4    	Player player = (Player)sender; //getting the player reference
5        player.sendMessage("Hello World!"); 
6    	return true;
7    }
8    return false;
9}