How to use RadioButtonGroup in Android?

in xml page:

< ?xml version="1.0" encoding="utf-8"?> 
< LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" > 
    < TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Which company do you like the most?"
        android:textSize="25dp"
        android:textStyle="bold" /> 
    < RadioGroup
        android:id="@+id/menu"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:checkedButton="@+id/lunch"
        android:orientation="vertical" > 
        < RadioButton
            android:id="@+id/google"
            android:checked="true"
            android:text="Google" /> 
        < RadioButton
            android:id="@+id/ms"
            android:text="Microsoft" /> 
        < RadioButton
            android:id="@+id/apple"
            android:text="Apple" /> 
        < RadioButton
            android:id="@+id/nokia"
            android:text="Nokia" /> 
        < RadioButton
            android:id="@+id/samsung"
            android:text="Samsung" /> 
    < /RadioGroup> 
    < TextView
        android:id="@+id/choice"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:text=""
        android:textSize="25dp" /> 
    < Button
        android:id="@+id/clear"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Clear CheckBoxes" /> 
< /LinearLayout> 

in Java Class:

public class Page Flipping extends Activity implements
        RadioGroup.OnCheckedChangeListener, View.OnClickListener {

    private TextView mChoice;
    private RadioGroup mRadioGroup;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_page_flipping);
        mRadioGroup = (RadioGroup) findViewById(R.id.menu);
        // test listening to checked change events
        mRadioGroup.setOnCheckedChangeListener(this);
        mChoice = (TextView) findViewById(R.id.choice);
        // test clearing the selection
        Button clearButton = (Button) findViewById(R.id.clear);
        clearButton.setOnClickListener(this);
    }

    public void onCheckedChanged(RadioGroup group, int checkedId) {
        if (checkedId == R.id.google) {
            mChoice.setText("Selected Google");
        }
        if (checkedId == R.id.ms) {
            mChoice.setText("Selected Microsoft");
        }
        if (checkedId == R.id.apple) {
            mChoice.setText("Selected Apple");
        }
        if (checkedId == R.id.nokia) {
            mChoice.setText("Selected Nokia");
        }
        if (checkedId == R.id.samsung) {
            mChoice.setText("Selected Samsung");
        }
    }

    public void onClick(View v) {
        mRadioGroup.clearCheck();
    }
}