MainActivity.java

public class MainActivity extends AppCompatActivity {
  private Realm mRealm;
  private RealmConfiguration mRealmConfig;
  private EditText mText;
  private RealmRecyclerView mNotes;
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
 
   mRealmConfig = new RealmConfiguration
                .Builder(this)
                .build();
   Realm.setDefaultConfiguration(mRealmConfig);
   mRealm = Realm.getDefaultInstance();
   mText = (EditText) findViewById(R.id.et_text);
   mNotes = (RealmRecyclerView) findViewById(R.id.rv_notes);
 
   Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
   setSupportActionBar(toolbar);
 
   FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
   fab.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
           Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                   .setAction("Action", null).show();
       }
   });
  }
}