Re: HttpURLConnection

From:

Eric Sosman <esosman@comcast-dot-net.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 19 Feb 2013 17:56:31 -0500

Message-ID:

<kg0vtf$jap$1@dont-email.me>

On 2/19/2013 4:45 PM, bob smith wrote:

How can people use the class HttpURLConnection when the abstract method connect() from URLConnection is never defined?

I thought you can't use a class till all the abstract blanks are filled in?

     The openConnection() method of the URL class returns a
URLConnection object. I haven't used it myself, but from the
documentation it appears that for an HTTP URL the URLConnection
will in fact be an HttpURLConnection.

     Both of those classes are abstract, and as such they cannot
be instantiated. The object actually returned will be an instance
of some concrete subclass, possibly anonymous. The inheritance
tree would look something like

    java.lang.Object
        java.net.URLConnection
            java.net.HttpURLConnection
                (maybe a few more levels here)
                    some.concrete.class.Thing

     If you're curious, you can do getClass() on the object you
get back from openConnection(), and print its class name or do
other snoopy things. But to use it, you're just fine treating
it as an HttpURLConnection -- because it "is an" HttpURLConnection,
in exactly the same way that an Integer "is a" Number.

--
Eric Sosman
esosman@comcast-dot-net.invalid