Android check null or empty string in Android

Question

In my trying AsyncTask I get email address from my server. In onPostExecute() I have to check is email address empty or null. I used following code to check it:

if (userEmail != null && !userEmail.isEmpty()) {     Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();     UserEmailLabel.setText(userEmail); } 

But in my Toast I see null is printed. My full code:

private class LoadPersonalData extends AsyncTask<String, Void, Void> {     @Override     protected void onPreExecute() {         super.onPreExecute();     }      protected Void doInBackground(String... res) {         List<NameValuePair> params = new ArrayList<NameValuePair>();         params.add(new BasicNameValuePair("user_id", PrefUserName));         params.add(new BasicNameValuePair("type", type_data));         JSONObject json = jsonParser.makeHttpRequest(Url, "POST", params);         String result = "";         try {             result = json.getString("message");         } catch (JSONException e) {             e.printStackTrace();         }         if (result.equals("success")) {             try {                 userEmail = json.getString("email");             } catch (JSONException e) {                 // TODO Auto-generated catch block                 e.printStackTrace();             }         }         return null;     }      @Override     protected void onPostExecute(Void result) {         // TODO Auto-generated method stub         super.onPostExecute(result);                     if (userEmail != null && !userEmail.isEmpty()) {             Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();             UserEmailLabel.setText(userEmail);         }     } 

How can I check for null and empty string?

Answer 1

Use TextUtils.isEmpty( someString )

String myString = null;  if (TextUtils.isEmpty(myString)) {     return; // or break, continue, throw }  // myString is neither null nor empty if this point is reached Log.i("TAG", myString); 

Notes

• The documentation states that both null and zero length are checked for. No need to reinvent the wheel here.
• A good practice to follow is early return.

Answer 2

From @Jon Skeet comment, really the String value is "null". Following code solved it

if (userEmail != null && !userEmail.isEmpty() && !userEmail.equals("null"))