public List<Group_schedule> getGroup_scheduleList(int group_id)
	{
		List<Group_schedule> list = new ArrayList<Group_schedule>();
		try {
			PreparedStatement ps = con.prepareStatement("SELECT * FROM group_schedule WHERE group_id=?");
			ps.setInt(1, group_id);
			ResultSet rs = ps.executeQuery();
			
			while(rs.next())
			{
				list.add(getGroup_scheduleFromRS(rs));
			}
			rs.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return list;
	}