public boolean fuelCheck(Player player, Material single, Material block) {

    Inventory fuelInventory = getFuelInventory(player);
    ItemStack rocketBoots = player.getInventory().getBoots();

    int fuelCost = 0;

    switch (rocketBoots.getType()) {
      case LEATHER_BOOTS:
        fuelCost = 1 + getBootPowerLevel(rocketBoots);
        break;

      case IRON_BOOTS:
        fuelCost = 2 + getBootPowerLevel(rocketBoots);
        break;

      case GOLD_BOOTS:
        fuelCost = 3 + getBootPowerLevel(rocketBoots);
        break;

      case DIAMOND_BOOTS:
        fuelCost = 4 + getBootPowerLevel(rocketBoots);
        break;
    }

    if (fuelInventory.containsAtLeast(new ItemStack(block), fuelCost)) return true;
    if (fuelInventory.containsAtLeast(new ItemStack(single), fuelCost)) return true;

    commonString.messageSend(
        RocketInit.getPlugin(),
        player,
        true,
        RocketLanguage.FuelRequired(single.name().toLowerCase()));
    RocketInit.rocketTimeout.add(player.getUniqueId());

    new BukkitRunnable() {
      int c = 5;

      @Override
      public void run() {
        if (c <= 0) {
          RocketInit.rocketTimeout.remove(player.getUniqueId());
          this.cancel();
          return;
        }
        player.setFlying(false);
        c--;
      }
    }.runTaskTimer(RocketInit.getPlugin(), 0, 20);

    return false;
  }