how to get info from user firebase android studio code example

Example 1: user login for android studio using firebase

auth.createUserWithEmailAndPassword(email, password).addOnCompleteListener(this, OnCompleteListener{ task ->
    if(task.isSuccessful){
        Toast.makeText(this, "Successfully Registered", Toast.LENGTH_LONG).show()
        val intent = Intent(this, MainActivity::class.java)
        startActivity(intent)
        finish()
    }else {
        Toast.makeText(this, "Registration Failed", Toast.LENGTH_LONG).show()
    }
})

Example 2: how to check the current user in firebase android

@Override
public void onStart() {
    super.onStart();
    FirebaseUser currentUser = mAuth.getCurrentUser();
    if (currentUser == null) {
        // No user is signed in
    } else {
        // User logged in
    }
}