//In basic.java onEnable()
pm.registerEvent(Event.Type.PLAYER_COMMAND, this.playerListener, Event.Priority.Monitor, this);
//In basicBlockListener.java BasicBlockListener
    public void onPlayerCommand(PlayerChatEvent event){
        String[] split = event.getMessage().split(" ");
        Player player = event.getPlayer();
        if (split[0].equalsIgnoreCase("/hiworld")){
            player.sendMessage("Hi world!");
        }
    }