public String getPIDByCoordinate(Statement statement,Double longitude,Double latitude)//根据坐标获取PID
	{
		String result = null;
		sql = "select PID from Park where longitude = '" + longitude +"' and latitude = '"+latitude+"'";
		try 
		{
			ResultSet rs = statement.executeQuery(sql);
			while (rs.next()) {
				result = rs.getString("PID");
			}
		} 
		catch (SQLException e) 
		{
			System.out.println("Error! (from src/Fetch/Park.getPIDByCoordinate())");
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return result;
	}