Not able to access google webservices its giving login required error in java

Question

I have enabled Google Play Android Developer API in developerconsole.Still i m getting login required error. I have created new key for server application and used the same as API KEY in webserivices

My Java Code:

package com.razak.sample;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class TestGoogleAPI {

    /**
     * @param args
     */
    public static void main(String[] args) {
        try {

            URL url = new URL("https://www.googleapis.com/androidpublisher/v1.1/applications/packageName/inapp/productId/purchases/token?key=AIza*************************");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept", "application/json");

            if (conn.getResponseCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : "
                        + conn.getResponseCode());
            }

            BufferedReader br = new BufferedReader(new InputStreamReader(
                (conn.getInputStream())));

            String output;
            System.out.println("Output from Server .... \n");
            while ((output = br.readLine()) != null) {
                System.out.println(output);
            }

            conn.disconnect();

          } catch (MalformedURLException e) {

            e.printStackTrace();

          } catch (IOException e) {

            e.printStackTrace();

          }

        }
}

Output:

{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "required",
    "message": "Login Required",
    "locationType": "header",
    "location": "Authorization"
   }
  ],
  "code": 401,
  "message": "Login Required"
 }
}