import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import java.util.Set;

public class Main {
    public static void main(String[] args) throws IOException{
        URL url = new URL("https://www.twle.cn");
        URLConnection conn = url.openConnection();

        Map headers = conn.getHeaderFields();
        Set<String> keys = headers.keySet();
        for( String key : keys ){
            String val = conn.getHeaderField(key);
            System.out.println(key+"    "+val);
        }
        System.out.println( conn.getLastModified() );
    }
}

Transfer-Encoding    chunked
null    HTTP/1.1 200 OK
Server    Tengine/1.3.0
Connection    keep-alive
Vary    Cookie
Date    Mon, 04 May 2015 03:54:05 GMT
X-Powered-By    PHP/5.3.15
Content-Type    text/html; charset=UTF-8