Twitter api request in android and getting the response code 401 message

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Android

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.twitterlayout);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
twitter_consumer_key= "";
twitter_consumer_secret="";
oauth_token = "";
oauth_token_secret = "";
q="India";
String get_or_post = "GET";
// This is the signature method used for all Twitter API calls
String oauth_signature_method = "HMAC-SHA1";
// generate any fairly random alphanumeric string as the "nonce". Nonce = Number used ONCE.
String uuid_string = UUID.randomUUID().toString();
uuid_string = uuid_string.replaceAll("-", "");
String oauth_nonce = uuid_string; // any relatively random alphanumeric string will work here
// get the timestamp
Calendar tempcal = Calendar.getInstance();
long ts = tempcal.getTimeInMillis();// get current time in milliseconds
String oauth_timestamp = (new Long(ts/1000)).toString(); // then divide by 1000 to get seconds
// assemble the proper parameter string, which must be in alphabetical order, using your consumer key

String parameter_string = "lang=en&oauth_consumer_key=" + twitter_consumer_key + "&oauth_nonce=" + oauth_nonce + "&oauth_signature_method=" + oauth_signature_method +
"&oauth_timestamp=" + oauth_timestamp + "&oauth_token=" + URLEncoder.encode(oauth_token) + "&oauth_version=1.0&q=" + URLEncoder.encode(q) + "&result_type=mixed";


Log.d("parameter_string=",parameter_string);
twitter_endpoint = "https://api.twitter.com/1.1/users/search.json";
twitter_url="https://api.twitter.com/1.1/users/search.json?q=india";

String signature_base_string = get_or_post + "&"+ URLEncoder.encode(twitter_endpoint) + "&" + URLEncoder.encode(parameter_string);
String oauth_signature = "";
try {
oauth_signature = computeSignature(signature_base_string, twitter_consumer_secret + "&");
}
catch (GeneralSecurityException e) {
e.printStackTrace();
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}

String authorization_header_string = "OAuth oauth_consumer_key=\"" + twitter_consumer_key + "\",oauth_signature_method=\"HMAC-SHA1\",oauth_timestamp=\"" + oauth_timestamp +
"\",oauth_nonce=\"" + oauth_nonce + "\",oauth_version=\"1.0\",oauth_signature=\"" + URLEncoder.encode(oauth_signature) + "\",oauth_token=\"" + URLEncoder.encode(oauth_token) + "\"";
Log.d("Header String",authorization_header_string);

URL url = null;
try
{
Log.d("Url",twitter_url);
url = new URL(twitter_url);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setDoInput(true);
urlConnection.setRequestMethod("GET");
urlConnection.setRequestProperty("Host", "api.twitter.com");
urlConnection.setRequestProperty("User-Agent", "Mozilla/5.0");
urlConnection.setRequestProperty("Authorization",authorization_header_string);
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
urlConnection.setUseCaches(false);
int responseCode = urlConnection.getResponseCode();
Log.d("Response Code :", String.valueOf(responseCode));
InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
StringBuilder builder = new StringBuilder();
String responsedata = null;
while ((inputString = bufferedReader.readLine()) != null) {
builder.append(inputString);
}

JSONObject topLevel = new JSONObject(jsonCallbackToJson(builder.toString()));
Log.d("Toplevel", builder.toStrin

g());
}
catch (MalformedURLException e) {
e.printStackTrace();
Log.i("URL-ERROR:",e.toString());
}
catch (IOException | JSONException e)
{
e.printStackTrace();
Log.i("IO-ERROR:", e.toString());
}
}

What I have tried:

i have tried the above code for twitter api using android httpurlconnection.It gives 401 response code.please help anyone how to make proper code