Error type 3 Activity class does not exist

try {
		String MYFILE = "my_file";
		String strText = "My text";

                // MODE_APPEND, MODE_WORLD_READABLE, MODE_WORLD_WRITEABLE
		// create new file or rewrite existing
                FileOutputStream fos = openFileOutput(MYFILE, getApplicationContext().MODE_PRIVATE);
                // append to file
                FileOutputStream fos = openFileOutput(MYFILE, getApplicationContext().MODE_APPEND);

		fos.write(strText.getBytes());
		fos.close();					
	} catch (IOException e) {
		e.toString();
    }	

try {
// new file    
BufferedWriter out = new BufferedWriter(
    		new FileWriter("outfilename"));
    // append text 
   BufferedWriter out = new BufferedWriter(new FileWriter("outfilename", true));
    out.write("some text");
    out.close();
 } catch (IOException e) {
   e.toString();
}			

import com.example.app.R

Resources res = getResources();
String sText = res.getString(R.string.app_name);

<resources>
    <string name="app_name">My app name</string>
</resources>

My text (<i>some text</i>) blah blah...
Change to:
My text (   <i>some text</i>) blah blah...

private void dialogModeFC() {
	try {
	final AlertDialog alertDialog =	new AlertDialog.Builder(MainActivity.this)
    .setTitle(R.string.select_dialog)
    //.setItems(
    .setSingleChoiceItems(R.array.select_dialog_items, -1
    		, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {

        /* User clicked so do some stuff 
        <item>Happy New Year</item>
        <item>Merry Christmas</item>
        <item>I Love You</item>
        */
            String[] items = getResources().getStringArray(R.array.select_dialog_items);
// list with boolean variables - which is true
//            for (int i = 0; i < _listMode.size(); i++) {
//            	_listMode.set(i, false);
//            }
//            _listMode.set(which, true);
            dialog.dismiss();
//            new AlertDialog.Builder(MainActivity.this)
//                    .setMessage("You selected: " + which + " , " + items[which])
//                    .show();
        }
    })
    .create();
	alertDialog.show();
	} catch (Exception e) {
		e.printStackTrace();
		Toast.makeText(getApplicationContext(), e.getMessage().toString(), Toast.LENGTH_LONG)
				.show();//("dialogModeFC", e.getMessage().toString());
	}
}// end dialogModeFC