Firebase Android Login

Login (e mail, password):

Java
auth.signInWithEmailAndPassword(email, password)
                    .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                        @Override
                        public void onComplete(@NonNull Task<AuthResult> task) {
                            if (!task.isSuccessful()) {
                                // there was an error
                                if (password.length() < 6) {
                                    Toast.makeText(getBaseContext(), "The password should be 6 characters at least!", Toast.LENGTH_SHORT).show();
                                } else {
                                    internetControl();
                                    Toast.makeText(getBaseContext(), "no membership found...", Toast.LENGTH_SHORT).show();
                                }
                                dialog.dismiss();
                            } else {
                                FirebaseUser user = auth.getCurrentUser();
                                updateUI(user);
                                Intent intent = new Intent(Login.this, MainActivity.class);
                                startActivity(intent);
                                finish();
                                dialog.dismiss();
                                Toast.makeText(getBaseContext(), "Successful Login", Toast.LENGTH_SHORT).show();
                            }
                        }
});


Depencies:
implementation 'com.google.firebase:firebase-auth:16.0.3'


Login  Token:

 @Override
    protected void onStart() {
        super.onStart();
        FirebaseUser currentUser = auth.getCurrentUser();
        updateUI(currentUser);
    }
    
    
FirebaseUser user = auth.getCurrentUser();
                                updateUI(user);
                                
                                 private void updateUI(FirebaseUser user) {
        if (user != null) {
            startActivity(new Intent(Login.this,MainActivity.class));
            finish();

        } else {
            Toast.makeText(Login.this,"hata",Toast.LENGTH_SHORT).show();
        }
    }

Exit:

 mauth.signOut();