Error

@Override
    public boolean onCommand (CommandSender sender, Command command, String label, String[]args){
        if (command.getName().equals("scan") && sender instanceof Player) {
            loadAllChunks(((Player) sender).getWorld()); //loading all chunks from mda files
            Chunk[] chunks = (((Player) sender).getWorld().getLoadedChunks());
            for (int i = 0; i < chunks.length; i++) {
                for (int j = 0; j < chunks[i].getX() * 16; j++) { //each block's x in a chunk
                    for (int k = 0; k < chunks[i].getZ() * 16; k++) { //each block's z in a chunk
                        for (int l = 0; l < 256; l++) { //each block's y in a chunk
                            Block block = chunks[i].getBlock(j, l, k);
                            if(block.getState() instanceof Sign){
                                Sign sign = (Sign) block.getState();
                                System.out.println("Found a sign at X " + block.getX() + " Y " + block.getY() + " Z " + block.getZ() + " with text \"" + Arrays.toString(sign.getLines()) + "\"");
                            }else System.out.println("Scanned X " + block.getX() + " Y " + block.getY() + " Z " + block.getZ() );

                        }
                    }
                }

            }
        }


        return true;
    }