Greet Caller by Name in Java

package pbxsampleapp;

import com.sun.net.httpserver.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class GreetCallerbyName 
{
   public static void main(String[] args)
    {
        try
        {
            phoneBook = new LinkedHashMap<>();
            phoneBook.put("+12345671", "John");
            phoneBook.put("1001", "Kevin");
            phoneBook.put("+12345675", "Jack");

            System.out.println("Starting http server...");
            HttpServer server = HttpServer.create(new InetSocketAddress(InetAddress.getByAddress(new byte[]{ 0, 0, 0, 0 }), 12345), 0);
            server.createContext("/greetcallerbyname", new PbxSampleApp.PBXRequestHandler());
            server.start();
            System.out.println("http server running on " + server.getAddress().toString());
        }
        catch (IOException ex) { System.out.println("Error" + ex.toString()); }
    }
    static Map<String, String> phoneBook;

    static class PBXRequestHandler implements HttpHandler
    {
        @Override
        public void handle(HttpExchange httpExchange) throws IOException
        {
            Map parameters = parseQuery(httpExchange.getRequestURI().getQuery());
            String callerName = "Sir or Madame";
            if (parameters.containsKey("Caller") && phoneBook.containsKey(parameters.get("Caller")) )
            {
                callerName = phoneBook.get(parameters.get("Caller").toString()).toString();
            }
            httpExchange.getResponseHeaders().add("Content-type", "text/xml");
            String response = "<?xml version=\"1.0\"?>"
                    + "<Response>"
                    + "<Speak>Hello " + callerName + "!</Speak>"
                    + "</Response>";
            httpExchange.sendResponseHeaders(200, response.length());
            OutputStream os = httpExchange.getResponseBody();
            os.write(response.getBytes());
            os.close();
        }

        private Map<String, String> parseQuery(String params) throws UnsupportedEncodingException
        {
            Map<String, String> query_pairs = new LinkedHashMap<String, String>();
            String[] pairs = params.split("&");
            String paramname;
            String value;
            for (String pair : pairs)
            {
                int idx = pair.indexOf("=");
                paramname = pair.substring(0, idx);
                value = pair.substring(idx + 1);
                query_pairs.put(paramname, value);
                System.out.println(String.format("%s: %s", paramname, value));
            }
            return query_pairs;
        }
    }
}