ArrowTracker

        @EventHandler
    private void onLaunch(final EntityShootBowEvent e) {
        // Make this your main class.
        final JavaPlugin plugin = this;

        if (e.getEntity() instanceof Player) {
            final Player p = (Player) e.getEntity();
            final List<ItemStack> arsenal = new ArrayList<ItemStack>();
            for (ItemStack item : p.getInventory().getContents()) {
                if (item != null && item.getType() == Material.ARROW) {
                    // Store all the arrows in the inventory.
                    arsenal.add(item.clone());
                }
            }
            new BukkitRunnable() {
                public void run() {
                    for (ItemStack item : arsenal) {
                        if (!p.getInventory().contains(item)) {
                            // This is the arrow ItemStack that was shot as it
                            // is no longer there exactly.
                            String name = item.getItemMeta().hasDisplayName() ? item.getItemMeta().getDisplayName() : "";
                            System.out.println("A(n) " + name + (name.isEmpty() ? "" : " ") + "arrow has been fired.");
                            e.getProjectile().setMetadata("ArrowTracker", new FixedMetadataValue(plugin, name));
                            return;
                        }
                    }
                }
            }.runTaskLater(plugin, 0L);
        }
    }

    @EventHandler
    private void onHit(EntityDamageByEntityEvent e) {
        List<MetadataValue> meta = e.getDamager().getMetadata("ArrowTracker");
        String nameMeta = "";
        for (MetadataValue value : meta) {
            // Where 'this' is your main class.
            if (value.getOwningPlugin().equals(this)) {
                nameMeta = value.asString();
                break;
            }
        }
        if (!nameMeta.isEmpty())
            System.out.println("An entity was damaged by a(n) " + nameMeta + " arrow");
    }