RadioButton RadioGroup Java Android example

import android.content.SharedPreferences;

public class MainClass extends Activity {
  public static final String PREFERENCES_NAME = "MyPrefsFile";
  String myNewString;
  int myNewInt;
  Boolean myNewBool;


   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // read old settings if exist
      SharedPreferences settings = getSharedPreferences(PREFERENCES_NAME, 0);
			
     String sDefault = "Hello!";
      String sStringFromPrefFile = settings.getString("myString", sDefault); // new text  or default Hello!
          
      int nDefaultIndex = 2; //
      int nIndexFromPrefFile = settings.getInt("myInt", nDefaultIndex); // 4 or default 2
			
      Boolean bDefault = false;
      Boolean bFromPrefFile = settings.getBoolean("silentMode", bDefault); // true or default false
        
        
        // new settings will saved in onStop or onPause
        myNewString = "new text";
        myNewInt = 4;
        myNewBool = true;
     }   

    @Override
    protected void onPause() {
    	super.onPause();
        Toast.makeText(getApplicationContext(), "onPause "
        		, Toast.LENGTH_SHORT).show();

    	savePreferences();
    }
    
    @Override
    protected void onStop() {
    	super.onStop();
    	savePreferences();
    }
    /**save settings*/	
    public void savePreferences(){
    	try {
    		SharedPreferences settings = getSharedPreferences(PREFERENCES_NAME, 0);
    		SharedPreferences.Editor editor = settings.edit();
 
    		editor.putString("myString", myNewString);
     		editor.putInt("nMyInt", myNewInt);
    		editor.putBoolean("silentMode", myNewBool); // 
    		
    		editor.commit();
    	} catch (Exception e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    	}
    	
    }	
}

public class MainActivity extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new SampleView(this));
	}

	private static class SampleView extends View {

		// CONSTRUCTOR
		public SampleView(Context context) {
			super(context);
			setFocusable(true);

		}
	       private static void makePath(Path p) {
	            p.moveTo(10, 0);
	            p.cubicTo(100, -50, 200, 150, 300, 0);
	        }
		@Override
		protected void onDraw(Canvas canvas) {

			canvas.drawColor(Color.CYAN);
			Paint p = new Paint();
			// smooths
			p.setAntiAlias(true);
			p.setColor(Color.RED);
			p.setStyle(Paint.Style.STROKE); 
			p.setStrokeWidth(5);
			// opacity
			//p.setAlpha(0x80);
 
			p.setColor(Color.BLACK);
			Path mPath = new Path();
            makePath(mPath);
			canvas.drawPath(mPath, p); //(rectF, 90, 45, true, p);
		}

	}
}

public class Main extends Activity {

private TextView mTextView;
private Activity mAct;
private Intent mIntent;

protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main_layout);
  mTextView = findViewById(R.id.mTextView);
  mAct = getActivity();
  mIntent = getIntent();
 }

}

public class Main extends Fragment{

 private TextView mTextView;
 private FragmentActivity mFrgAct;
 private Intent mIntent;
 private LinearLayout mLinearLayout;
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
          Bundle savedInstanceState) {
          View root = inflater.inflate(R.layout.fragment_main, null);
        return root;
    }

 public void onViewCreated(View view, Bundle savedInstanceState) {
          // you can add listener of elements here
          /*Button mButton = (Button) view.findViewById(R.id.button);
            mButton.setOnClickListener(this); */
          mTextView = view.findViewById(R.id.mTextView);
          mLinearLayout = (LinearLayout)view;
 }
 public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
          mFrgAct = getActivity();
          mIntent = mFrgAct.getIntent(); //  Intent intent = new Intent(getActivity().getIntent());
 }

}

// image from res/drawable
	int resID = getResources().getIdentifier("my_image", 
			"drawable", getPackageName());
// view
	int resID = getResources().getIdentifier("my_resource", 
			"id", getPackageName());

// string
	int resID = getResources().getIdentifier("my_string", 
			"string", getPackageName());

// List passed as reference JAVA
List<Integer>list = new ArrayList<Integer>();

public void fc (List<Integer>listRef){
listRef.add(7);
listRef.add(5);
}
fc(list); // 7, 5 


// String passed as reference JAVA
	public void mutate(AtomicReference<Object> ref) { ref.set("Goodbye"); }

		AtomicReference<Object> ref = new AtomicReference<Object>("Hello");
		mutate(ref);
		System.out.println(ref.get()); //Goodbye!
             String s = (String) ref.get();


// Integer passed as reference JAVA
	private static void mutate(AtomicReference<Object> ref) { ref.set(7); }

	//public static void main(String[] arg) {
		AtomicReference<Object> ref = new AtomicReference<Object>(5);
		mutate(ref);
		System.out.println(ref.get()); // 7
int n = (Integer) ref.get();


// Float passed as reference JAVA
	private static void mutate(AtomicReference<Object> ref) { ref.set(14.8f); }

	//public static void main(String[] arg) {
		AtomicReference<Object> ref = new AtomicReference<Object>(12.1f);
		mutate(ref);
		float f = (Float) ref.get();
		System.out.println(f); //14.8