public void put(Object obj, WeakReference<Object> wr)
		{
			Long id = (long) System.identityHashCode(obj);
			List<WeakReference<Object>> bucket = buckets.get(id);
			if (bucket == null)
			{
				bucket = new ArrayList<>();
				buckets.put(id, bucket);
			}
			synchronized (bucket)
			{
				if (!bucket.contains(wr))
				{
					bucket.add(wr);
				}
			}
		}