URL openStream

OReilly.Java.I.O.2nd.Edition
5.1. URLs

		InputStream in = null;
		try {
			URL u = new URL("http://www.oreilly.com/");
			in = u.openStream();
			for (int c = in.read(); c != -1; c = in.read()) {
				System.out.write(c);
			}
		} catch (MalformedURLException ex) {
				
		} finally {
			if (in != null)
				in.close();
		}

	

Most network connections, even on LANs, are slower and less reliable sources of data than files. Connections across the Internet are even slower and less reliable, and connections through a modem are slower and less reliable still. One way to enhance performance under these conditions is to buffer the data: to read as much data as you can into a temporary storage array inside the class, then parcel it out as needed. In the next chapter, you'll learn about the BufferedInputStream class that does exactly this.

Untrusted code running under the control of a security manager e.g., applets that run inside a web browser are normally allowed to connect only to the host they were downloaded from. This host can be determined from the URL returned by the getCodeBase( ) method of the Applet class. Attempts to connect to other hosts throw security exceptions. You can create URLs that point to other hosts, but you may not download data from them using openStream( ) or any other method. (This security restriction for applets applies to any network connection, regardless of how you get it.)


5.2. URL Connections

URL connections  are closely related to URLs, as their name implies. Indeed, you get a reference to a URLConnection by using the openConnection( )  method of a URL object; in many ways, the URL class is only a wrapper around the URLConnection class. URL connections provide more control over the communication between the client and the server.