public static void destroy() {
        try
        {
	    if(stm == null) {
		System.out.println("stm is null");
		return;
	    } else {
		stm.close();
	    }
	    if(con == null) {
		System.out.println("con is null");
		return;
	    } else {
		con.close();
	    }
            connected = false;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }