public List<Bill> selectBill(){
		connectionDB();
		String sql=" select * from bill";
		List<Bill> bills=new ArrayList<Bill>();
		try {
			ps=conn.prepareStatement(sql);
			rs=ps.executeQuery();
			Bill bill=null;
			while(rs.next()){
				bill=new Bill();
				bill.setBillId(rs.getLong("billId"));
				bill.setGoodsName(rs.getString("goodsName"));
				bill.setGoodsNum(rs.getInt("goodsNum"));
				bill.setMoney(rs.getDouble("money"));
				bill.setIsPay(rs.getString("isPay"));
				bill.setSupplierName(rs.getString("supplierName"));
				bill.setGoodsDescrible(rs.getString("goodsDescrible"));
				bill.setBillTime(rs.getDate("billtime"));
				bills.add(bill);		
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			closeDB();
		}
		return bills;
		
	}