Java Reference
In-Depth Information
Reader
r
=
new
InputStreamReader
(
in
);
int
c
;
while
((
c
=
r
.
read
())
!=
-
1
)
{
System
.
out
.
print
((
char
)
c
);
}
System
.
out
.
println
();
}
}
catch
(
IOException
ex
)
{
System
.
err
.
println
(
ex
);
}
}
}
}
Here's the result. First, you see the default value: midnight, January 1, 1970, GMT, con‐
verted to Pacific Standard Time. Next, you see the new time, which you set to 24 hours
prior to the current time:
%
java Last24 http://www.elharo.com
Original if modified since: Wed Dec 31 19:00:00 EST 1969
Will retrieve file if it's modified since Sat Jun 01 11:11:27 EDT 2013
Because this document hasn't changed in the last 24 hours, it is not reprinted.
protected boolean useCaches
Some clients, notably web browsers, can retrieve a document from a local cache, rather
than retrieving it from a server. Applets may have access to the browser's cache. Stand‐
alone applications can use the
java.net.ResponseCache
class. The
useCaches
variable
determines whether a cache will be used if it's available. The default value is
true
,
meaning that the cache will be used;
false
means the cache won't be used.Because
useCaches
is
protected
, programs access it using the
getUseCaches()
and
setUseCaches()
methods:
public
void
setUseCaches
(
boolean
useCaches
)
public
boolean
getUseCaches
()
This code fragment disables caching to ensure that the most recent version of the docu‐
ment is retrieved by setting
useCaches
to
false
:
try
{
URL
u
=
new
URL
(
"http://www.sourcebot.com/"
);
URLConnection
uc
=
u
.
openConnection
();
uc
.
setUseCaches
(
false
);
// read the document...
}
catch
(
IOException
ex
)
{
System
.
err
.
println
(
ex
);
}
Two methods define the initial value of the
useCaches
field,
getDefaultUseCaches()
and
setDefaultUseCaches()
:
