public class MainActivity extends AppCompatActivity {
      public static RadioGroup tapRadioGroup, timeRadioGroup;
      ...
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);

          tapRadioGroup = findViewById(R.id.finger_radio_group);
          timeRadioGroup = findViewById(R.id.time_radio_group);
          ...
          }
  }

public void getTapCheckedOption() {
        RadioGroup radioGroup = MainActivity.tapRadioGroup;
        ...
    }

public void getTimeCheckedOption() {
        RadioGroup radioGroup = MainActivity.timeRadioGroup;
        ...
    }