@Override throws "method does not override method from its superclass" error.

public class MainListActivity extends ListActivity {

    protected String[] mBlogPostTitles;
    public static final int NUMBER_OF_POSTS = 20;
    public static final String TAG = MainListActivity.class.getSimpleName();
    protected JSONObject mBlogData;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_list);

        if (isNetworkAvailable()) {
            GetBlogPostTask getBlogPostTask = new GetBlogPostTask();
            getBlogPostTask.execute();
        }
        else {
            Toast.makeText(this, "Network is Unavailable", Toast.LENGTH_LONG).show();
        }
        //Toast.makeText(this, getString(R.string.no_items), Toast.LENGTH_LONG).show();
    }

    private boolean isNetworkAvailable() {
        ConnectivityManager manager = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = manager.getActiveNetworkInfo();
        boolean isAvailable = false;
                if (networkInfo != null && networkInfo.isConnected()){
            isAvailable = true;
        }
        return isAvailable;
        }

    private void updateList() {
        if (mBlogData == null){
            //TODO: Handle error
        }
        else{
            try {
                Log.d(TAG,mBlogData.toString(2));
            } catch (JSONException e) {
                Log.e(TAG, "Exception error caught!",e);
            }
        }
    }

    private class GetBlogPostTask extends AsyncTask<Object, Void, JSONObject> {

        @Override
        protected JSONObject doInBackground(Object[] objects) {
            int responseCode = -1;
            JSONObject jsonResponse = null;

            try {
            URL blogFeedUrl = new URL("http://blog.teamtreehouse.com/api/get_recent_summary/?count=" + NUMBER_OF_POSTS);
            HttpURLConnection connection = (HttpURLConnection) blogFeedUrl.openConnection();
            connection.connect();

                responseCode = connection.getResponseCode();
                if (responseCode == HttpURLConnection.HTTP_OK){
                    InputStream inputStream = connection.getInputStream();
                    Reader reader = new InputStreamReader(inputStream);
                    int contentLength = connection.getContentLength();
                    char[] charArray = new char[contentLength];
                    reader.read(charArray);
                    String responseData = new String(charArray);
                    jsonResponse = new JSONObject(responseData);
                }
                else {
                    Log.i(TAG, "Unsuccessful Http Response Code:" + responseCode);
                }
        }
        catch(MalformedURLException e) {
            Log.e(TAG, "Exception caught: ", e);
        }
        catch (IOException e){
            Log.e(TAG, "Exception caught: ", e);
        }
        catch (Exception e){
            Log.e(TAG, "Exception caught: ", e);
        }
            return jsonResponse;
        }

        @Override
        protected void OnPostExecute(JSONObject result){
            mBlogData = result;
            updateList();

        };
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_list, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}