求解socket服务的空值有关问题

/**     * 注册处理     */    @SuppressWarnings( { "unchecked", "deprecation" })    private void serverRegiste() {        try{            int flag=0; //是否重名判断标志            Register_Customer clientMessage=(Register_Customer)obj;            File flist=new File("user.txt");            if(flist.length()!=0){//判断是否是第一个注册用户                ObjectInputStream objInput=new ObjectInputStream(new FileInputStream(flist));                vList=(Vector)objInput.readObject();                //判断是否有重名                for(int i=0;i<vList.size();i++){                    Register_Customer reg=(Register_Customer)vList.elementAt(i);                    if(reg.custName.equals(clientMessage.custName)){                        toClient.println("用户名已经存在，请重新输入");                        flag=1;                        break;                    }                    if(reg.custName.equals("所有人")){                        toClient.println("禁止使用此用户名,请另外选择");                        flag=1;                        break;                    }                    if(reg.custName.equals("admin")||reg.custName.equals("Administrator")){                        toClient.println("禁止使用此用户名,请另外选择");                        flag=1;                        break;                    }                }            }            if(flag==0){                // 添加新注册用户                vList.addElement(clientMessage.custName+"注册成功");                //将量中的类写回到文件中                FileOutputStream file=new FileOutputStream(flist);                ObjectOutputStream objout=new ObjectOutputStream(file);                objout.writeObject(vList);                                //发送注册成功信息                toClient.println(clientMessage.custName+"注册成功");                Date t=new Date();                log("用户"+clientMessage.custName+"注册成功,"+"注册时间:"+t.toLocaleString()+"\n");                file.close();                objout.close();                formClient.close();            }        }catch (ClassNotFoundException e) {            System.out.println(e);        }catch (IOException e) {            System.out.println(e);        }    }    

//连接到服务器            Socket toServer;            toServer=new Socket(strServerIp,1001);            ObjectOutputStream streamToServer=new ObjectOutputStream(toServer.getOutputStream());            //写客户详细资料到服务器socket            streamToServer.writeObject((Register_Customer)rc);            //读取自服务器socket的状态            BufferedReader formServer=new BufferedReader(new InputStreamReader(toServer.getInputStream()));            String status=formServer.readLine();            //显示成功消息            JOptionPane op=new JOptionPane();            op.showMessageDialog(null, status);            if(status.equals(rc.custName+"注册成功")){                txtUserName.setText("");                pwdPassword.setText("");                pwdConfirmPass.setText("");                txtAge.setText("");                txtEmail.setText("");            }