public class AnvilListener implements Listener {

  @EventHandler
  public boolean onPlayerInteract(PlayerInteractEvent e) {
    if (checkEvent(e)) {
      Player p = e.getPlayer();
      List<Block> lastTwoTargetBlocks = p.getLastTwoTargetBlocks(null, 5);
      Block prevBlock = lastTwoTargetBlocks.get(0);
      Block targetBlock = lastTwoTargetBlocks.get(1);
      if (targetBlock.getType().equals(Material.ANVIL) && prevBlock.getType().equals(Material.AIR)) {
        ItemStack item = e.getItem();
        Material type = item.getType();
        if (type.equals(Material.ACTIVATOR_RAIL)) {
          prevBlock.setType(type);
          if (targetBlock.getData == 0 || targetBlock.getData == 2) {
            prevBlock.setData(0);
          } else if (targetBlock.getData == 1 || targetBlock.getData == 3) {
            prevBlock.setData(1);
          }
        }
        ItemUtil.removeItemFromPlayer(p, item); // Helper method I have to remove 1 item from a player's inventory
      }
    }
  }

  private boolean checkEvent(PlayerInteractEvent e) {
    if (e.getAction().equals(Action.RIGHT_CLICK_BLOCK) && e.hasItem() && e.hasBlock()) {
      if (e.getItem.getType() == Material.ACTIVATOR_RAIL) return true;
    }
    return false;
  }

}