protected boolean alreadyin(string tname,string colname, string value)

    {      

        int result;

        resultset rst=null;

        try {

        //执行sql语句

        string query = "select "+colname+" from "+tname+" where "+colname+"='"+value+"'";

        statement statement = connformax.createstatement();

        rst = statement.executequery( query );

        if(rst.next())

        {

            statement.close();

            rst.close();

            return true;

        }      

     }

     catch ( sqlexception sqlex ) {

        sqlex.printstacktrace();

        return false;

     }

     return false;    

    }