private boolean isObsidianDoor(Block b)
  {
    Block up = b.getRelative(BlockFace.UP);
    Block down = b.getRelative(BlockFace.DOWN);
    Block east = b.getRelative(BlockFace.EAST);
    Block west = b.getRelative(BlockFace.WEST);
    Block north = b.getRelative(BlockFace.NORTH);
    Block south = b.getRelative(BlockFace.SOUTH);
    if (up.getType() == Material.IRON_DOOR_BLOCK)
    {
      Block otherWest = up.getRelative(BlockFace.WEST);
      Block otherEast = up.getRelative(BlockFace.EAST);
      Block otherNorth = up.getRelative(BlockFace.NORTH);
      Block otherSouth = up.getRelative(BlockFace.SOUTH);
      up = up.getRelative(BlockFace.UP);
    }
    else if (down.getType() == Material.IRON_DOOR_BLOCK)
    {
      Block otherWest = down.getRelative(BlockFace.WEST);
      Block otherEast = down.getRelative(BlockFace.EAST);
      Block otherNorth = down.getRelative(BlockFace.NORTH);
      Block otherSouth = down.getRelative(BlockFace.SOUTH);
      down = down.getRelative(BlockFace.DOWN);
    }
    else
    {
      return false;
    }
    Block otherSouth;
    Block otherNorth;
    Block otherEast;
    Block otherWest;
    if ((up.getTypeId() == 49) && (down.getTypeId() == 49) &&
      (east.getTypeId() == 49) && (west.getTypeId() == 49) &&
      (otherWest.getTypeId() == 49) && (otherEast.getTypeId() == 49)) {
      return true;
    }
    if ((up.getTypeId() == 49) && (down.getTypeId() == 49) &&
      (north.getTypeId() == 49) && (south.getTypeId() == 49) &&
      (otherNorth.getTypeId() == 49) && (otherSouth.getTypeId() == 49)) {
      return true;
    }
    return false;
  }

  @EventHandler
  public void onEntityExplode(EntityExplodeEvent event)
  {
    List<Block> destroy = event.blockList();
    Iterator<Block> it = destroy.iterator();
    while (it.hasNext())
    {
      Block b = (Block)it.next();
      if ((b.getType() == Material.IRON_DOOR_BLOCK) &&
        (isObsidianDoor(b))) {
        it.remove();
      }
    }
  }