List all Response Header

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

public class Header extends HttpServlet 
{

 public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
  {
	
	PrintWriter out=response.getWriter();
	try 
	{
		//Here Refresh is servlet in which refresh header is set to 5 Second using setHeader("Refresh",5)	
		URL obj = new URL("http://localhost:8080/Refresh");
		URLConnection conn = obj.openConnection();
		Map<String, List<String>> map = conn.getHeaderFields();
 
		out.println("Printing Response Header...\n");
 
		for (Map.Entry<String, List<String>> entry : map.entrySet()) 
		{
				out.println("Key : " + entry.getKey() + " ,Value : " + entry.getValue());
		}
 
		out.println("\nGet Response Header By Key ...\n");
		String server = conn.getHeaderField("Server");
 
		if (server == null) 
		{
			out.println("Key 'Server' is not found!");
		} 
		else 
		{
			out.println("Server - " + server);
		}
 
		out.println("\n Done");
 
    } 
	catch (Exception e) 
	{
		e.printStackTrace();
    }
  }
  // Method to handle POST method request.
  public void doPost(HttpServletRequest request,
                     HttpServletResponse response)
      throws ServletException, IOException {
     doGet(request, response);
  }
}