Java static variable issue-CodePudding

I'm experiencing issue with couple static variables.

I have a datastore class named LoginDataStore with the following codes:

class LoginDataStore {
    private static String userEmail;
    private static String userPass;
    
    public LoginDataStore(String userEmail, String userPassword) {
        LoginDataStore.setUserEmail(userEmail);
        LoginDataStore.setUserPassword(userPassword);
    }
    
    public static void setUserEmail(String email) {
        LoginDataStore.userEmail = email;
    }
    
    public static String getUserEmail() {
        return LoginDataStore.userEmail;
    }
    
    public static void setUserPassword(String password) {
        LoginDataStore.userPass = password;
    }
    
    public static String getUserPassword() {
        return LoginDataStore.userPass;
    }
}

and the main thread will set those 2 variables when the user press "login" button, using this function:

            if (loginThreadIsRunning) {
                loginThreadIsRunning = false;
            }
LoginDataStore loginDataStore = new LoginDataStore(emailInput.getText(), String.valueOf(passwordInput.getPassword()));

Then i initialize the thread:

        LoginThread lt = new LoginThread();
        Thread t1 = new Thread(lt);
        t1.start();

the thread has this codes:

class LoginThread extends LoginUI implements Runnable{  
    public void run() {
        LoginUI loginUI = new LoginUI();
        if (!loginUI.loginThreadIsRunning) {
            loginUI.loginThreadIsRunning = true;
            System.out.println("[LoginThread] has started.");
            String loginEmail = LoginDataStore.getUserEmail();
            String loginPass = LoginDataStore.getUserPassword();
            System.out.println("[LoginThread] loginEmail: "   loginEmail   " | loginPass: "   loginPass);
            loginUI.loginThreadIsDone = true;
        }
    }
}

It's currently just for debugging before i implement the backend server.

However, when i try to login the first time, the Thread outputs the data correctly, but if i try to login again, the output is simply empty, same is for if i don't change the data but just repress the login button, but also if i do change the details in the login UI.

Example output:

[LoginThread] has started.
[LoginThread] loginEmail: test | loginPass: null
[LoginThread] has started.
[LoginThread] loginEmail:  | loginPass: null

Does anyone know what may cause this issue?

CodePudding user response：

In your code, you are not storing the 'userPassword'. You are overring the password with the email.

public LoginDataStore(String userEmail, String userPassword) {
        LoginDataStore.setUserEmail(userEmail);
        LoginDataStore.setUserEmail(userPassword);  //<- Here
    }

Implement function to setPassword and modify the constructor.

    public LoginDataStore(String userEmail, String userPassword) {
        LoginDataStore.setUserEmail(userEmail);
        LoginDataStore.setUserPassword(userPassword);
    }
    
    public static void setUserPassword(String userPassword) {
        LoginDataStore.userPass = userPassword;
    }

CodePudding user response：

Try removing the static modifier from your instance variables inside your LoginDataStore class. A static variable belongs to the class and not a particular instance.

Leaving the instance variables as non-static variables will allow you to create multiple instances of LoginDataStore with unique or same values for the userEmail and userPass

More on this here https://www.baeldung.com/java-static-variables-initialization#:~:text=In Java, static variables are,(non-static variables).