public class CopyBlock implements CommandExecutor {

    // it copies starting from the minimum block on x, y and z
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {

        if (sender instanceof Player) {

            Player player = (Player) sender;

            // parse arguments
            double[] pos = new double[9];

            if (args.length != 9) {
                player.sendMessage("Invalid arguments amount.");
            }
            else {
                for (int i = 0; i < pos.length; i++) {
                    pos[i] = Double.parseDouble(args[i]);
                }
            }

            // create the cube to be copied
            BoundingBox box = new BoundingBox(pos[0], pos[1], pos[2], pos[3], pos[4], pos[5]);

            // get the world
            World world = player.getWorld();

            // start copying
            for (double x = box.getMinX(); x <= box.getMaxX(); x++) {
                for (double y = box.getMinY(); y <= box.getMaxY(); y++) {
                    for (double z = box.getMinZ(); z <= box.getMaxZ(); z++) {

                        //----------------
                        // copy the block
                        //----------------

                        // point to that block
                        Location location = new Location(world, x, y, z);

                        // get the block at that location
                        Block block = location.getBlock();

                        // get block type and some other stuff
                        BlockData blockData = block.getBlockData();
                        String blockString = blockData.getAsString();

                        //-----------------
                        // paste the block
                        //-----------------

                        // point to the destiny block
                        Location newLocation = new Location(world, pos[6] + (x - box.getMinX()), pos[7] + (y - box.getMinY()), pos[8] + (z - box.getMinZ()));

                        // get the block at the new location
                        Block newBlock = newLocation.getBlock();

                        // set the new block data
                        BlockData newBlockData = Bukkit.createBlockData(blockString);
                        newBlock.setBlockData(newBlockData);

                        //-------------------
                        // handle containers
                        //-------------------

                        // get the old block state
                        BlockState blockState = block.getState();

                        // check if it's a container
                        if (blockState instanceof Container) {

                            // get the contents of the container
                            Inventory inventory = ((Container)blockState).getInventory();

                            // get the inventory of the destiny block
                            Inventory newInventory = ((Container)newBlock.getState()).getInventory();

                            // put items on the new block
                            for (ItemStack item : inventory) {
                                if (item != null)
                                    newInventory.addItem(item);
                            }
                        }
                    }
                }
            }
        }

        return true;
    }
}