Java HttpURLConnection class Program
- by pandu
I am learning java. Here is the sample code of HttpURLConnection class usage in some text book
import java.net.*;
import java.io.*;
import java.util.*;
class HttpURLDemo
{
public static void main(String args[]) throws Exception {
URL hp = new URL("http://www.google.com");
HttpURLConnection hpCon = (HttpURLConnection) hp.openConnection();
// Display request method.
System.out.println("Request method is " +
hpCon.getRequestMethod());
// Display response code.
System.out.println("Response code is " +
hpCon.getResponseCode());
// Display response message.
System.out.println("Response Message is " +
hpCon.getResponseMessage());
// Get a list of the header fields and a set
// of the header keys.
Map<String, List<String>> hdrMap = hpCon.getHeaderFields();
Set<String> hdrField = hdrMap.keySet();
System.out.println("\nHere is the header:");
// Display all header keys and values.
for(String k : hdrField) {
System.out.println("Key: " + k +
" Value: " + hdrMap.get(k));
}
}
}
Question is
Why hpCon Object is declared in the following way?
HttpURLConnection hpCon = (HttpURLConnection) hp.openConnection();
instead of declaring like this
HttpURLConnection hpCon = new HttpURLConnection();
Author provided the following explanation. I cant understand
Java provides a subclass of URLConnection that provides support for HTTP connections.
This class is called HttpURLConnection. You obtain an HttpURLConnection in the same
way just shown, by calling openConnection( ) on a URL object, but you must cast the result
to HttpURLConnection. (Of course, you must make sure that you are actually opening an
HTTP connection.) Once you have obtained a reference to an HttpURLConnection object,
you can use any of the methods inherited from URLConnection
