for(int i=id-data.size();i>0;i--) data.add(null);
for (int i = id - data.size(); i > 0; i--) { data.add(null); }
	public int put(int id, Object o) throws IllegalArgumentException {		if (id < 0) throw new IllegalArgumentException();		//make sure there is sufficient space to overlay		for(int i=id-data.size();i>0;i--) data.add(null);		data.add(id, o);		return id;	}