set support action bar error in androidx code example

Example: create method setsupportactionbar

import android.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v7.widget.Toolbar;


public class rutaActivity extends AppCompactActivity {

private Toolbar toolbar;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_ruta);

    getSupportActionBar().hide();//Ocultar ActivityBar anterior

    toolbar = (Toolbar) findViewById(R.id.app_bar);
    setSupportActionBar(toolbar); //NO PROBLEM !!!!