Method threw 'java.lang.NullPointerException' exception. Cannot evaluate com.android.okhttp.Headers.toString()

Question

OS:Mac + android-studio

1. httpsURLConnection.connect() Cannot evaluate com.android.okhttp.Headers.toString()

   package com.mar.android.photogallery;

   import android.net.Uri; import android.util.Log;

   import java.io.BufferedReader; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.security.cert.X509Certificate;

   import javax.net.ssl.HttpsURLConnection; import javax.net.ssl.SSLContext; import javax.net.ssl.TrustManager; import javax.net.ssl.X509TrustManager;

   import org.apache.commons.lang3.StringUtils;

   /**

   • Created by marares on 2018/4/9. */

   public class FlickrFetchr { private static final String TAG = "FlickrFetchr"; private static final String API_KEY = "****";

   public void fetchItems() {
       HttpsURLConnection httpsURLConnection = null;
       BufferedReader reader = null;
       try {
           URL url = new URL("https://api.flickr.com/services/rest/?method=flickr.photos.getRecent&api_key=***&format=json&nojsoncallback=1&extras=url_s");
           System.out.println("1====================");
           httpsURLConnection = (HttpsURLConnection) url.openConnection();
           httpsURLConnection.setConnectTimeout(5000);
           httpsURLConnection.setDoInput(true);
           httpsURLConnection.setUseCaches(false);
           System.out.println("2====================");
   
           httpsURLConnection.connect();//<----Cannot evaluate com.android.okhttp.Headers.toString()
           System.out.println("3====================");
           System.out.println(httpsURLConnection.getResponseCode());
           System.exit(0);
   
           reader = new BufferedReader(new InputStreamReader(httpsURLConnection.getInputStream()));
           StringBuilder sBuilder = new StringBuilder();
           String line;
           while ((line = reader.readLine()) != null) {
               sBuilder.append(line);
           }
           Log.e("TAG", "content=" + sBuilder.toString());
       } catch (MalformedURLException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       } finally {
           if (httpsURLConnection != null) {
               httpsURLConnection.disconnect();
           }
   
           if (reader != null) {
               try {
                   reader.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
       }
   
   }
   

   }