登录如何使用相同的代码为Java中的不同用户输入密码？

Question

（注意：我不熟悉Java和编程，也不熟悉使用Netbeans）

我的任务是创建代码，它将首先要求输入用户名，然后要求输入密码。我的解决方案是为每个用户的密码输入提供一个单独的代码块。然而，这是非常漫长的。我用于输入密码的代码如下：

List<String> passwords = new ArrayList<>();   //array which is populated by user input
    Scanner passwordinput = new Scanner(System.in);

    do {
        System.out.print("Create password? (y/n)");        //create password request
        if (passwordinput.next().startsWith("y")) {
            System.out.print("Create password (no spaces): ");
            passwords.add(passwordinput.next());
        } else {
            break;
        }
    } while (true);

    System.out.print("Enter password: ");                    //enter password request
    String enterpass;
    enterpass = passwordinput.next();

    if (passwords.contains(enterpass)) {
        System.out.println("wohoo you're in");
    } else {
        System.out.println("bad luck brudda");
    }

总之，我询问用户是否想要创建密码，然后他们输入密码（输入字符串）。然后，他们被要求输入该密码以继续

有没有什么方法可以让我为每个用户使用相同的代码块，但不必每次都复制它

任何其他改进都是受欢迎的

Answer 1

看看地图。在HashMap中，将一个值映射到一个固定键。因此，每个用户名（密钥）只能存在一次，但密码（值）可以始终相同
你需要一个HashMap。这个HashMap有一个字符串作为键，一个字符串作为值。密钥是你的用户名，密码是你的值。所以你这样做：

HashMap<String, String> logins = new HashMap<String, String>();
String username1 = "FIRST_USERNAME";
String password1 = "FIRST_PASSWORD";
String username2 = "SECOND_USERNAME";
String password2 = "SECOND_PASSWORD";
logins.put(username2, password2);
logins.put(username1, password1); // adds the username and the password to your "loginlist"
String inputUser = scanner.nextLine();    
String inputPassword = scanner.nextLine();
if(inputPassword.equals(logins.get(inputUser)){
 // Password and user correct
}

编辑：
下面是一个如何使用方法的示例。也许你那时更明白。希望你对例外情况有所了解。如果不是的话，你应该了解它们，因为它们对java来说是必不可少的

public class LoginManager {

private Map<String, String> logins;

public LoginManager() {
    this.logins = new HashMap<String, String>();
}

public void logIn(final String pUserName, final String pPassword) {
    if (pPassword == null) {
        throw new IllegalArgumentException("No password given");
    }
    if (!pPassword.equals(this.logins.get(pUserName))) {
        throw new IllegalStateException("Wrong username or password");
    }
}

public void registerUser(final String pUserName, final String pPassword) {
    if (pUserName != null && pPassword != null) {
        if (!pUserName.isEmpty() && !pPassword.isEmpty()) {
            if (!this.logins.containsKey(pUserName)) {
                this.logins.put(pUserName, pPassword);
                return;
            }
        }
        else {
            throw new IllegalStateException("Username already in use");
        }
    }
    throw new IllegalArgumentException("Username or password not given");
}

public static void main(final String[] args) {
    final String choice1 = "1";
    final String choice2 = "2";
    LoginManager manager = new LoginManager();
    Scanner input = new Scanner(System.in);
    boolean loginTried = false;
    while (!loginTried) {
        System.out.print("Register new user(1) or login (2): ");
        switch (input.nextLine()) {
            case choice1:
                System.out.print("New username: ");
                String userName = input.nextLine();
                System.out.print("Password: ");
                String password = input.nextLine();
                try {
                    manager.registerUser(userName, password);
                    System.out.println("User registered");
                }
                catch (Exception error) {
                    System.out.println(error.getMessage());
                }
                break;
            case choice2:
                loginTried = true;
                System.out.print("Username: ");
                String loginName = input.nextLine();
                System.out.print("Password: ");
                String loginPassword = input.nextLine();
                try {
                    manager.logIn(loginName, loginPassword);
                    System.out.println("Login was successfully");
                }
                catch (Exception error) {
                    System.out.println("Login failed: " + error.getMessage());
                }
                break;
            default:
                System.out.println("Invalid choice. Choose 1 or 2");
                break;
        }
    }
    input.close();
 }
}