Java登录开发遇类型不匹配错误，求比较器实现指导

Hey there! Let's work through your two main problems: the type mismatch error and implementing the login comparison logic. I'll break this down step by step.

1. Fixing the "incompatible types" Error #

The root cause here is a mismatch between what your User constructor expects and what you're passing it:

• Your User class has a constructor that takes two String parameters: public User(String username, String password)
• But in UserList, you're trying to pass an int as the second argument with Integer.parseInt(res[1])

Since your Logins.txt stores passwords as strings (like "Password"), you don't need to convert it to an integer. Additionally, your file has a space after the comma (e.g., Test, Password), so splitting on commas will leave a leading space in your password string—we'll fix that with trim() to avoid mismatches later.

Here's the corrected UserList class:

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

public class UserList {
    private ArrayList<User> loginList;

    // Initialize the list in the constructor instead of taking it as a parameter
    public UserList() {
        loginList = new ArrayList<>();
        Scanner sc;
        try {
            sc = new Scanner(new File("F:\\Cours\\[ISIS 2A]\\Projet Programmation\\BoiteDeJeux\\src\\boitedejeux\\Logins.txt"));
            // Fix: Don't skip the first line with an extra sc.nextLine()
            while (sc.hasNextLine()) {
                String ligne = sc.nextLine();
                String[] res = ligne.split(",");
                // Trim to remove leading/trailing spaces from username and password
                String username = res[0].trim();
                String password = res[1].trim();
                // Pass two Strings to the User constructor (no Integer conversion!)
                loginList.add(new User(username, password));
            }
        } catch (FileNotFoundException e) {
            System.out.println("Error: Could not find Logins.txt file.");
            e.printStackTrace();
        }
    }

    // Add a getter to access the login list from other classes
    public ArrayList<User> getLoginList() {
        return loginList;
    }
}

Key fixes here:

• Removed the ArrayList<User> parameter from the UserList constructor and initialized the list internally
• Fixed the loop to not skip the first line of your file
• Used trim() to clean up whitespace from the split values
• Removed Integer.parseInt() for the password, passing the cleaned string directly to the User constructor

2. Implementing the Login Comparison Logic #

Now we need to add the loginCheck method to your BoiteDeJeux class. This method will:

1. Create a UserList instance to load all stored credentials
2. Loop through each user in the list
3. Compare the user's input against stored username and password
4. Return/print a success or failure message

Here's the updated BoiteDeJeux class:

import java.util.Scanner;

public class BoiteDeJeux {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String username;
        String password;

        System.out.print("Enter your username: ");
        username = input.nextLine().trim(); // Trim user input to avoid whitespace issues

        System.out.print("Enter your password: ");
        password = input.nextLine().trim();

        loginCheck(username, password);
        input.close(); // Don't forget to close the scanner!
    }

    private static void loginCheck(String inputUsername, String inputPassword) {
        UserList userList = new UserList();
        boolean isLoggedIn = false;

        for (User user : userList.getLoginList()) {
            // Compare both username and password
            if (user.getUsername().equals(inputUsername) && user.getPassword().equals(inputPassword)) {
                isLoggedIn = true;
                break; // Exit the loop once a match is found
            }
        }

        if (isLoggedIn) {
            System.out.println("Login successful! Welcome back.");
        } else {
            System.out.println("Login failed: Invalid username or password.");
        }
    }
}

3. Quick Note on Your Logins.txt #

Make sure each credential pair is on a separate line (your current example shows Test, Password Test2, Password2 which might be a typo). It should look like this:

Test, Password
Test2, Password2

That's it! With these changes, your type mismatch error will be gone, and the login logic will correctly compare user input against the stored credentials.

内容的提问来源于stack exchange，提问作者Tameiki