Java Reference
In-Depth Information
The output is:
http:
//www.ncsa.uiuc.edu/HTMLPrimer.html#GS is the same file as
http:
//www.ncsa.uiuc.edu/HTMLPrimer.html#HD
Conversion
URL
has three methods that convert an instance to another form:
toString()
,
toExternalForm()
, and
toURI()
.
Like all good classes,
java.net.URL
has a
toString()
method. The
String
produced
by
toString()
is always an absolute URL, such as
http://www.cafeaulait.org/javatuto‐
rial.html
. It's uncommon to call
toString()
explicitly. Print statements call
to
String()
implicitly. Outside of print statements, it's more proper to use
toExternal
Form()
instead:
public
String
toExternalForm
()
The
toExternalForm()
method converts a
URL
object to a string that can be used in an
HTML link or a web browser's Open URL dialog.
The
toExternalForm()
method returns a human-readable
String
representing the
URL. It is identical to the
toString()
method. In fact, all the
toString()
method does
is return
toExternalForm()
.
Finally, the
toURI()
method converts a
URL
object to an equivalent
URI
object:
public
URI
toURI
()
throws
URISyntaxException
We'll take up the
URI
class shortly. In the meantime, the main thing you need to know
is that the
URI
class provides much more accurate, specification-conformant behavior
than the
URL
class. For operations like absolutization and encoding, you should prefer
the
URI
class where you have the option. You should also prefer the
URI
class if you need
to store URLs in a hashtable or other data structure, since its
equals()
method is not
blocking. The
URL
class should be used primarily when you want to download content
from a server.
The URI Class
A URI is a generalization of a URL that includes not only Uniform Resource Locators
but also Uniform Resource Names (URNs). Most URIs used in practice are URLs, but
most specifications and standards such as XML are defined in terms of URIs. In Java,
URIs are represented by the
java.net.URI
class. This class differs from the
java.net.URL
class in three important ways:
