Trapdoor 1.12

            /*
            List<Block> processingDoors = new ArrayList<>();
            Block b = PlayerInteractEvent#getClickedBlock();
            */
            if(b.getType() == Material.TRAP_DOOR)
            {
                final BlockState bs = b.getState();
                final Location loc = b.getLocation();

                TrapDoor door = (TrapDoor) bs.getData();
                boolean open = door.isOpen();

                if(!open) // if it's closed before interact
                    processingDoors.add(b);
                else if(processingDoors.contains(b))
                    processingDoors.remove(b);

                new BukkitRunnable()
                {
                    public void run()
                    {      // to avoid a BlockBreakEvent check
                        if(b.getWorld().getBlockAt(loc).getType() == Material.TRAP_DOOR && processingDoors.contains(b)) // called
                        {
                            door.setOpen(!open);
                            bs.setData(door);
                            bs.update();
                        }
                    }

                }.runTaskLater(Main.getInstance(), 3 * 20L);
            }