Validate or Check if RadioGroup RadioButtons are not Checked ?

RadioGroup rg = (RadioGroup) findViewById(R.id.radioGroup);

int radioButtonId = rg.getCheckedRadioButtonId();

                        if (radioButtonId == -1) {

                              Toast.makeText(getApplicationContext(),

                                          "Please select atleast one option", 3000).show();

                        }

                        else {

          RadioButton radioButton = (RadioButton) findViewById(radioButtonId);

                              String radioValue = radioButton.getText().toString();

                              Toast.makeText(getApplicationContext(), radioValue, 3000)

                                          .show();

                        }