当我运行代码时，它没有呈现我期望的内容

Question

我试图在main Method中调用构造函数，但一直收到错误，我不知道为什么我会遇到这个问题，如果不调用构造函数，程序会运行，但不会显示任何内容，当我尝试调用它new EmailList((时；它也犯了一个需要字符串的错误，我试着在里面添加字符串，但仍然不起作用，

private BufferedReader br;
private Connection conn;
private Statement stmt;
private String emailadd;
private String accname;
private Random rc;
private String[] acc_name = {"John michael","Christopher Binlayan","Lancelot Binlayan","Jerry Damoyan","Jonathan Kedawen"};
private Integer numlength = acc_name.length;
private Integer useracc;

public EmailLists(String username,String Password)throws Exception
{
username = "root";
Password = "root";
Class.forName(Driver1);
Class.forName(Driver2);
conn =DriverManager.getConnection(URL,username,Password);
stmt = conn.createStatement();
br = new BufferedReader(new InputStreamReader(System.in));
rc = new Random();
start();
}
public void start()throws Exception
{
useracc = rc.nextInt(numlength);
System.out.println("Enter Email Address to be notified:");
emailadd=br.readLine();
String insertinto =("Insert Into EMAIL_LIST(EMAIL ADDRESS) VALUES ('"+emailadd+"')");
stmt.executeUpdate(insertinto);
System.out.println("Succesfully Added!! Welcome Username: "+acc_name[useracc]+"");
}

public static void main(String[] args){
new EmailLists(String username,String password);

}

}

Answer 1

您已经编写了

DriverManager.getConnection(URL,username,Password)

它编译得很好。请注意，你所做的只是传递你想要的论点。我建议你对构造函数也这样做

new EmailLists(username, password);

即重复已经奏效的方法。

BTW在使用这些变量之前，需要将其设置为某个值，或者您可以只给它们值。

new EmailLists("myusername", "mypassword");

注意：由于您在构造函数中定义了这些值，因此不需要传递它们。

public EmailLists() throws Exception
{
String username = "root";
String password = "root";

然后呼叫

new EmailLists();