Android Studio lock unlock file make read only or writable

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);

		}
		@Override
		protected void onDraw(Canvas canvas) {
			//drawARGB (int a, int r, int g, int b)
//			a  alpha component (0..255) of the color to draw onto the canvas 
//			r  red component (0..255) 
//			g  green component (0..255)  
//			b  blue component (0..255)  

			canvas.drawARGB(255, 0, 255, 10); 
		}

	}
}

public class MainClass {
	public static void main(String[] arg) {
		String[] arrayOfString = { "Hello", "people", "hello", "world!" };
		OuterLoop: for (int e = 0; e < 4; e++) {
			for (int i = 0; i < arrayOfString.length; i++) {
				if (arrayOfString[i].equals("hello"))
					continue OuterLoop;
				System.out.println(arrayOfString[i]);
			}
		}
	}
}
/*
Hello
people
Hello
people
Hello
people
Hello
people
*/

		Drawable dr = getResources().getDrawable(R.drawable.algebra);
		int h = dr.getIntrinsicHeight();
		int w = dr.getIntrinsicWidth();

		Bitmap ball = BitmapFactory.decodeResource(getResources(), R.drawable.algebra);
		int _nWidth = ball.getWidth();
		int _nHeight = ball.getHeight();

public void alertMy(String sTitle, String sMessage){
	AlertDialog.Builder builder = new AlertDialog.Builder(Test.this); // activity
  builder.setTitle(sTitle)
  .setMessage(sMessage)
  .setCancelable(false)
  .setNegativeButton("Close",new DialogInterface.OnClickListener() {
      public void onClick(DialogInterface dialog, int id) {
          dialog.cancel();
      }
  });
  AlertDialog alert = builder.create();
  alert.show();

}

public void updateList() {
		Context ctx = getActivity();
		Notes notes = new Notes(ctx);

		String[] from = { Notes.COLUMN_TITLE };
		int[] to = { android.R.id.text1 };
		int layout = Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ?
				android.R.layout.simple_list_item_activated_1 : android.R.layout.simple_list_item_1;
		ListAdapter adapter = new SimpleCursorAdapter(ctx,
				layout, notes.getNotes(), from,
				to, 0);

		setListAdapter(adapter);

		notes.close();
	}

/..................
@Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        
        // Set the item as checked to be highlighted when in two-pane layout
        getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        getListView().setItemChecked(position, true);
     
    }