Weeping Angels for Bukkit

public class WeepingAngelsMain extends JavaPlugin implements Listener {
    private Set< UUID > angels = new HashSet< UUID >();
    private Set< UUID > statues = new HashSet< UUID >();

    private Set< String > worlds = new HashSet< String >();
    private boolean blacklist;
    private double dotProductMax = 0;   // Ranges from -1 to 1 with 1 being directly in line of sight
    private int speedAmplifier = 10;
    private boolean ignoreCreativeAndSpectator = true;

    BukkitRunnable entityManager = new BukkitRunnable() {
        @Override
        public void run() {
            for ( Iterator< UUID > it = angels.iterator(); it.hasNext(); ) {
                Entity entity = Bukkit.getEntity( it.next() );
                if ( entity == null ) {
                    it.remove();
                    continue;
                }
                if ( !( worlds.contains( entity.getWorld().getName() ) ^ blacklist ) ) {
                    return;
                }
                boolean isStatue = false;
                for ( Player player : Bukkit.getOnlinePlayers() ) {
                    if ( player.hasPermission( "weepingangels.bypass" ) ) {
                        continue;
                    }
                    if ( ( player.getGameMode() == GameMode.CREATIVE || player.getGameMode() == GameMode.SPECTATOR ) && ignoreCreativeAndSpectator ) {
                        continue;
                    }
                    if ( !entity.getWorld().getUID().equals( player.getWorld().getUID() ) ) {
                        continue;
                    }
                    Vector toMob = entity.getLocation().subtract( player.getLocation() ).toVector().normalize();
                    Vector facing = player.getLocation().getDirection();
                    if ( facing.dot( toMob ) > dotProductMax && player.hasLineOfSight( entity ) ) {
                        if ( !statues.contains( entity.getUniqueId() ) ) {
                            statues.add( entity.getUniqueId() );
                            editEntity( entity, true );
                        }
                        isStatue = true;
                        break;
                    }
                }
                if ( !isStatue && statues.contains( entity.getUniqueId() ) ) {
                    statues.remove( entity.getUniqueId() );
                    editEntity( entity, false );
                }
            }
        }
    };

    @Override
    public void onEnable() {
        saveDefaultConfig();
        loadConfig();
        Bukkit.getPluginManager().registerEvents( this, this );
        for ( World world : Bukkit.getWorlds() ) {
            for ( Entity entity : world.getEntities() ) {
                if ( isStatue( entity ) ) {
                    angels.add( entity.getUniqueId() );
                }
            }
        }
        entityManager.runTaskTimer( this, 0, 1 );
    }

    private void loadConfig() {
        FileConfiguration config = YamlConfiguration.loadConfiguration( new File( getDataFolder() + "/config.yml" ) );
        dotProductMax = config.getDouble( "dot-product-maximum" );
        speedAmplifier = config.getInt( "monster-speed" );
        ignoreCreativeAndSpectator = config.getBoolean( "ignore-creative-and-spectator" );
        worlds.addAll( config.getStringList( "worlds" ) );
        blacklist = config.getBoolean( "world-blacklist" );
    }

    @EventHandler
    public void onEntitySpawnEvent( EntitySpawnEvent event ) {
        if ( isStatue( event.getEntity() ) ) {
            angels.add( event.getEntity().getUniqueId() );
        }
    }

    @EventHandler
    public void onEntityDie( ExplosionPrimeEvent event ) {
        Entity entity = event.getEntity();
        if ( statues.contains( entity.getUniqueId() ) && entity instanceof LivingEntity ) {
            ( ( LivingEntity ) entity ).removePotionEffect( PotionEffectType.SPEED );
        }
    }

    public boolean isStatue( Entity entity ) {
        return entity instanceof Monster;
    }

    public void editEntity( Entity entity, boolean lookingAt ) {
        if ( lookingAt ) {
            NBTEditor.setEntityTag( entity, ( byte ) 1, "NoAI" );
            if ( entity instanceof LivingEntity && entity instanceof Monster ) {
                LivingEntity monster = ( LivingEntity ) entity;
                monster.removePotionEffect( PotionEffectType.SPEED );
            }
        } else {
            NBTEditor.setEntityTag( entity, ( byte ) 0, "NoAI" );
            if ( entity instanceof LivingEntity && entity instanceof Monster ) {
                LivingEntity monster = ( LivingEntity ) entity;
                monster.addPotionEffect( new PotionEffect( PotionEffectType.SPEED, 1000000, speedAmplifier, true ), true );
            }
        }
    }
}