How to reset the loop when the loop found the matched username and password?

This code section is part of code in my program. I am currently write a GUI program. This part of code is about to extract the username and password from the ArrayList and if matched then user are allowed to login. My desired output is if this loop find the matched username and password, it will break and proceed to another interface; Oppositely, if didn't matched, the loop will continue to find the matched one. So then, how should my if-else going to be ? I can't pop up the message that show username and password is wrong because in else block, I need it to loop until find the matched.

public void actionPerformed(ActionEvent e){
        
        if(e.getSource() == loginButton){           
            for(int i =0;i<AcademicSystem.allUser.size();){
                User usr = AcademicSystem.allUser.get(i);
                User pswrd = AcademicSystem.allUser.get(i);
                
                System.out.println(usr.getLogin_username() + "\t" + userName.getText());
                System.out.println(pswrd.getLogin_password() + "\t"  + password.getText());
                System.out.println("");
                
                if(userName.getText().equals(usr.getLogin_username())&&password.getText().equals(pswrd.getLogin_password())){
                    JOptionPane.showMessageDialog(loginButton,"Username and password matched!");
                    JOptionPane.showMessageDialog(loginButton, "User[" + userName.getText() + "] have successfully logged in");
           
                    Dashboard db = new Dashboard();
                    setVisible(false);
                    db.setVisible(true);
                    break;
                }
                
                else if (!AcademicSystem.allUser.contains(userName.getText())&&!AcademicSystem.allUser.contains(password.getText())){
                   i++;
                }
            }
        }
    }

Don't try and do everything in you loop. Until the loop ends, you don't actually know what action you should take, so, instead, loop through the available users and find one which matches the criteria or, if you can't, let the match remain null.

Then when the loop ends, you can check the state of the matched object and take appropriate action.

For example:

User matchedUser = null;

String userName = this.userName.getText();
String password = this.password.getText();
for (User user : AcademicSystem.allUser) {
    if (userName.equals(usr.getLogin_username()) && password.equals(pswrd.getLogin_password())) {
        matchedUser = user;
        break;
    }
}

if (matchedUser != null) {
    // You're good to go
} else {
    // Authentication failed
}

This approach would all you to move the logic to the AcademicSystem and would then allow you to reduce the call to something more like:

User matchedUser = AcademicSystem.authenticate(userName.getText(), password.getText());
if (matchedUser != null) {
    // You're good to go
} else {
    // Authentication failed
}

This moves the responsibility for validating the user to the domain it belongs in and reduces you overall code complexity in the process, win/win