Mine

/**
 * 
 */
package net.sf.l2j.gameserver.experimental;

import javolution.util.FastCollection;
import javolution.util.FastCollection.Record;
import javolution.util.FastList;
import javolution.util.FastSet;
import net.sf.l2j.Config;
import net.sf.l2j.gameserver.model.L2Character;
import net.sf.l2j.gameserver.model.L2Object;
import net.sf.l2j.gameserver.model.L2PcInstance;
import net.sf.l2j.gameserver.model.L2Summon;
import net.sf.l2j.gameserver.model.L2World;
import net.sf.l2j.util.Point3D;

/**
 * @author Layane
 *
 */
public class NpcKnownList
{
    public static final long MINIMUM_UPDATE_DISTANCE_SQUARED = Config.MINIMUM_UPDATE_DISTANCE * Config.MINIMUM_UPDATE_DISTANCE;
    
    protected final FastSet<L2PcInstance> _knownPlayers = new FastSet<L2PcInstance>();
    protected final FastSet<L2Summon> _knownSummons = new FastSet<L2Summon>();
    
    protected final L2Character _owner;
    
    protected Point3D lastPosition;
    
    
    public NpcKnownList(L2Character owner)
    {
        _owner = owner;
    }
    
    protected static void checkKnownList(FastList<L2Object> out, FastCollection in)
    {
        for(Record r = in.head(),end = in.tail(); (r = r.getNext()) != end;)
        {
            L2Object object = (L2Object)in.valueOf(r);
            
            if (object != null)
                out.add(object);
            else
                in.delete(r);
        }
    }
    
    protected synchronized static void checkKnownList(FastCollection in)
    {
        for(Record r = in.head(),end = in.tail(); (r = r.getNext()) != end;)
        {
            L2Object object = (L2Object)in.valueOf(r);
            
            if (object == null)
                in.delete(r);
        }
    }
    
    public synchronized void addObject(L2Object object)
    {
        if (object == null || !_owner.isVisible())
            return;

    	if (knowsObject(object))
    	{
    		if (!object.isVisible())
    			_owner.removeKnownObject(object);
    		
    		return;
    	}

		if (_owner.getDistance(object.getX(), object.getY()) > _owner.getDistanceToWatchObject(object))
			return;
        
        if (object instanceof L2PcInstance)
        {
            _knownPlayers.add((L2PcInstance)object);
        }
        else if (object instanceof L2Summon)
        {
            _knownSummons.add((L2Summon)object);
        }
    }
    
    public synchronized void addPlayer(L2PcInstance player)
    {
        if (player == null || !_owner.isVisible())
            return;

    	if (knowsPlayer(player))
    	{
    		if (!player.isVisible())
    			_owner.removeKnownPlayer(player);
    		
    		return;
    	}

		if (_owner.getDistance(player.getX(), player.getY()) > _owner.getDistanceToWatchObject(player))
			return;
		
		_knownPlayers.add(player);
    }
    
    public synchronized void addSummon(L2Summon summon)
    {
        if (summon == null || !_owner.isVisible())
            return;

    	if (knowsSummon(summon))
    	{
    		if (!summon.isVisible())
    			_owner.removeKnownSummon(summon);
    		
    		return;
    	}

		if (_owner.getDistance(summon.getX(), summon.getY()) > _owner.getDistanceToWatchObject(summon))
			return;
		
		_knownSummons.add(summon);
    }
    
    public boolean knowsObject(L2Object object)
    {
        if (object == null)
        {
            //Do nothing
        }
        else if (object instanceof L2PcInstance)
        {
            _knownPlayers.contains((L2PcInstance)object);
        }
        else if (object instanceof L2Summon)
        {
            _knownSummons.contains((L2Summon)object);
        }
        
        return false;
    }
    
    public boolean knowsPlayer(L2PcInstance player)
    {
        if (player != null)
            return _knownPlayers.contains(player);
        return false;
    }
    
    public boolean knowsSummon(L2Summon summon)
    {
        if (summon != null)
            return _knownSummons.contains(summon);
        return false;
    }
    
    public final FastCollection<L2PcInstance> getAllKnownPlayers()
    {
        checkKnownList(_knownPlayers);
        return _knownPlayers.unmodifiable();
    }
    
    public final FastCollection<L2Summon> getAllKnownSummons()
    {
        checkKnownList(_knownSummons);
        return _knownSummons.unmodifiable();
    }
    
    public final FastCollection<L2Object> getAllKnownObjects()
    {
        FastList<L2Object> result = new FastList<L2Object>();
        
        synchronized(this)
        {
            checkKnownList(result, _knownPlayers);
            checkKnownList(result, _knownSummons);
        }
        
        return result.unmodifiable();
    }
    
    public synchronized void removeKnownObject(L2Object object)
    {
        if (object == null)
        {
            //Do nothing
        }
        else if (object instanceof L2PcInstance)
        {
            _knownPlayers.remove((L2PcInstance)object);
        }
        else if (object instanceof L2Summon)
        {
            _knownSummons.remove((L2Summon)object);
        }
    }
    
    public synchronized void removePlayer(L2PcInstance player)
    {
    	if (player != null)
    		_knownPlayers.remove(player);
    }
    
    public synchronized void removeSummon(L2Summon summon)
    {
    	if (summon != null)
    		_knownSummons.remove(summon);
    }
    
    public void clear()
    {
        _knownPlayers.clear();
        _knownSummons.clear();
    }
    
    public void updateKnownObjects()
    {
        
        synchronized (this)
        {
            Point3D worldPosition = _owner.getWorldPosition();
            if (worldPosition.distanceSquaredTo(lastPosition) <= MINIMUM_UPDATE_DISTANCE_SQUARED)
                return;
            
            lastPosition.setTo(worldPosition);
        }
        
        forgetDistantObjects();
        findCloseObjects();
    }
    
    private void forgetDistantObjects()
    {
        for (L2Object object : getAllKnownObjects())
        {
            if (!object.isVisible())
            {  
                _owner.removeKnownObject(object);  
            }
            else if (_owner.getDistance(object.getX(),object.getY()) > _owner.getDistanceToForgetObject(object))
            {
                _owner.removeKnownObject(object);
                object.removeKnownObject(_owner);
            }   
        }
        
    }
    
    private void findCloseObjects()
    {
        if (_owner.isDead() || !_owner.isVisible())
            return;

        for (L2Object object : L2World.getInstance().getVisibleObjects(_owner))
        {
            if (object != null)
            {
                _owner.addKnownObject(object, null);
                object.addKnownObject(_owner, null);
            }
        }
    }
    
}