OAuth authentication 2.0(3LO)

[Anandhakrishnan]

I want to authenticate third party application into jira.I got Client Id and Client secret, with this I have generated authorization code.But for 

Exchange authorization code for access token

I used the below code:

String url1="grant_type=authorization_code&client_id=Z6k7drhI5Imruu7UBAXCo4zImlUHUz14&client_secret=9P46D0ZB6vdqaS7Q9IIdBl9q0FLfLJ4RjgV3Kv95F1V8PYBjc6aHvK8GvinV4jRg&code=6Xay_ZrDVhRRa1qW&redirect_uri=http://localhost:8080";
url = new URL("https://auth.atlassian.com/oauth/token");
URLConnection conn = url.openConnection();
HttpURLConnection http=(HttpURLConnection)conn;
((HttpURLConnection) conn).setRequestMethod("POST");
conn.setDoOutput(true);
conn.setRequestProperty("Content-Type", "application/json");
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
System.out.println("Write1");
writer.write(url1);
System.out.println("Write2");
System.out.println("Response code:" + ((HttpURLConnection) conn).getResponseCode());
System.out.println("Response message:" + ((HttpURLConnection) conn).getResponseMessage());

writer.flush();

BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
while ((line = reader.readLine()) != null) {
System.out.println(line);
sb.append(line);
}

lineV = sb.toString();

writer.close();
reader.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

But I got an error like this:

Server returned HTTP response code: 401 for URL: https://auth.atlassian.com/oauth/token

Could you please anyone assist me to resolve this issue?