@Override
	public long getMass()
	{
		final long mass=this.mass;
		if(mass<0)
		{
			int newMass=phyStats().weight();
			for(final Enumeration<Room> r=getProperMap(); r.hasMoreElements();)
			{
				final Room R=r.nextElement();
				if(R!=null)
				{
					for(int i=0;i<R.numItems();i++)
					{
						final Item I=R.getItem(i);
						if(I!=null)
							newMass += I.phyStats().weight();
					}
					for(int i=0;i<R.numInhabitants();i++)
					{
						final MOB M=R.fetchInhabitant(i);
						if(M!=null)
							newMass += M.phyStats().weight();
					}
				}
			}
			this.mass=newMass;
		}
		return mass;
	}