DBConnectionManager 连接问题

protected Connection conn = null;        //Connection接口
    protected Statement stmt = null;        //Statement接口
    protected ResultSet rs = null;        //记录结果集
    protected PreparedStatement prepstmt = null;    //PreparedStatement接口
    protected String sqlStr;        //sql String
    protected boolean isConnect=true;    //与数据库连接标识
   
    public DataBase() {
        try
        {
            //数据库连接池包括一个管理类DBConnectionManager
            sqlStr = "";
            DBConnectionManager dcm = new DBConnectionManager();
            conn = dcm.getConnection();//这儿老是提示错误！
            stmt = conn.createStatement();
        }
    这儿老是提示错误！