Java Reference
In-Depth Information
Once the
package
is created, you can use the appropriate
import
command in your
program to make use of the
class
. For example, to use the
class
Clock
, as created in
the preceding code, you use the following
import
statement in your program:
import
jpfpatpd.Appendix.clockPackage.Clock;
In Java,
package
is a reserved word.
Example D-1 further explains how to use a package in a program. We assume that
the
has
been
compiled
and
placed
in
the
subdirectory
class
Clock
c:\jpfpatpd\Appendix\clockPackage
.
EXAMPLE D-1
The following program uses the
class
Clock
.
import
jpfpatpd.Appendix.clockPackage.Clock;
public class
TestClock
{
public static void
main(String[] args)
{
Clock myClock =
new
Clock(12,30,45);
System.out.println("myClock: " + myClock);
}
}
Because this program uses the
class
Clock
, when you compile the program using the
compiler command, you use the option
-classpath
to specify where to find the
compiled code of the
class
Clock
. Suppose that the file
TestClock.java
is in the
subdirectory
c:\jpfpatpd
. Consider the following command:
javac -classpath c:\ TestClock.java
This command finds
Clock.class
in the subdirectory
c:\jpfpatpd\Appendix\clockPackage
. The compiled code
TestClock.class
of
the program
TestClock.java
is placed in the current subdirectory. On the other hand,
the following command places the compiled code,
TestClock.class
, in the subdir-
ectory
c:\jpfpatpd
:
javac -d c:\jpfpatpd -classpath c:\ TestClock.java
Suppose the file
TestClock.class
is in the subdirectory
c:\jpfpatpd
. The following
command executes the program
TestClock.class
:
java -classpath .;c:\ TestClock
If you are using an IDE to create Java programs, you need to be familiar with the
commands to compile and execute them. Typically, an IDE automatically stores the
compiled code of the classes in an appropriate subdirectory.
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