而循环以不匹配的用户名/密码退出

Question

所以这只是我的程序的一小部分，但本质上我要做的是在循环时进行基本的身份验证。我不确定我是否应该使用 while 循环或其他东西。
我希望程序做的只是在用户名和密码与"帐户"匹配时停止循环。
我不确定这个问题是否清楚，但这是我能做的最好的事情。如果您需要任何澄清，请告诉我。

编辑：如果我输入错误的用户名或密码，它不会再次循环。这是我的问题。

这是我遇到问题的部分：

User user2 = new User();
        userList.add(user2);
        String userLogin = "estebangong23";
        String userPass = "twitterisfun";
        String existingUserName = " ";
        String existingPassWord = " ";
        user2.setUserName("estebangong23");
        user2.setEmailAddress("[e-mail]");
        user2.setPassWord("twitterisfun");
        System.out.println("Please sign in here.");
        while (!existingUserName.equals("estebangong23") && existingPassWord.equals("twitterisfun")) {
            System.out.println("Username: ");
            existingUserName = sc.nextLine().toLowerCase();
            System.out.println("Enter your password: ");
            existingPassWord = sc.nextLine().toLowerCase();
            //System.out.println("Log In unsuccessful. Incorrect username or password.");
        } 

以下是我的大部分程序：

    import java.util.*;
    import java.io.*;
    public class MyClass {
    public static void main(String args[]) {
    // make it so u can log in to an existing account
    // make it double check the password and email
    Scanner sc = new Scanner(System.in);
    List<User> userList = new ArrayList<User>();
    List<String> matchesList = new ArrayList<String>();
    String date = "03/21/2019";
    String tweet = " ";
    System.out.println("-------------------------------------------------------------------------");
    System.out.println("|                               Twitter                                 |");
    System.out.println("| Sign Up                                                        Log in |");
    System.out.println("-------------------------------------------------------------------------");
    System.out.println("Would you like to Log In or Sign Up?");
    String responseString = sc.nextLine().toLowerCase();

    if (responseString.equals("signup") ) {
        User user1 = new User(); //this creates the first user
        System.out.println("Alright, lets get started by setting up your profile!");
        System.out.println("Please enter a username.");
        user1.setUserName(sc.nextLine());
        System.out.println("Please enter your email address.");
        user1.setEmailAddress(sc.nextLine());
        System.out.println("Please enter a password.");
        user1.setPassWord(sc.nextLine());
        System.out.println("Alright we got your account all setup. Just take a moment to review everthing. Don't worry you can change this stuff later if you want!");
        user1.printUserProfile();
        userList.add(user1);
        System.out.println("Your account is all setup, go ahead and try posting something for the first time!");

        } else { //end signup if
        User user2 = new User();
        userList.add(user2);
        String userLogin = "estebangong23";
        String userPass = "twitterisfun";
        String existingUserName = " ";
        String existingPassWord = " ";
        user2.setUserName("estebangong23");
        user2.setEmailAddress("[e-mail]");
        user2.setPassWord("twitterisfun");
        System.out.println("Please sign in here.");
        while (!existingUserName.equals("estebangong23") && existingPassWord.equals("twitterisfun")) {
            System.out.println("Username: ");
            existingUserName = sc.nextLine().toLowerCase();
            System.out.println("Enter your password: ");
            existingPassWord = sc.nextLine().toLowerCase();
            //System.out.println("Log In unsuccessful. Incorrect username or password.");
        } 
        } //end else
    //main program
    System.out.println("-------------------------------------------------------------------------");
    System.out.println("Let's post something! Show the world what your thinking about righ now!");
    System.out.println("If you want to stop entering tweets at any time, please enter '**'. ");
    System.out.println(" ");
    while (!tweet.equals("**")) {
        System.out.println("Enter your tweet here: ");
        tweet = sc.nextLine().toUpperCase();
        String[] tweetArray = tweet.split(" ");
        System.out.println("");


    } //end tweet while loop

    System.out.println("-------------------------------------------------------------------------");
    } //end main
    } //end main class
    class User {
    // this class sets up the users profile when they are signing up
private String userName;
private String emailAddress;
private String passWord;
public List<Tweet> tweetList = new ArrayList<Tweet>();
//Username, Age, Email Address, Tweets[ ]
//Methods
//Setters and getters, Create tweet
public User () {
}
public String getUserName() {return this.userName;}
public void setUserName(String userName) {this.userName = userName;}
public String getEmailAddress() {return this.emailAddress;}
public void setEmailAddress(String emailAddress) {this.emailAddress = emailAddress;}
public String getPassWord() {return this.passWord;}
public void setPassWord(String passWord) {this.passWord = passWord;}
public void printUserProfile() {
    System.out.println("Username: " + this.userName);
    System.out.println("Email Address: " + this.emailAddress);
    System.out.println("Password (remember not to share this to anyone) " + this.passWord);
}

}

Answer 1

简单地回答你的问题，

while (! (existingUserName.equals(userLogin) && existingPassWord.equals(userPass)) ) { // if users doesn't exist
...
}

但是，您需要重新考虑用于身份验证的代码。我猜你才刚刚开始。首先将它们放在表中，然后使用 PreparedStatement 访问它们。