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This application consists of three separate source files located in three different packages. Together they illustrates the use ofpackage and import directives, along with javac to build a standalone Java application consisting of classes in three separatepackages.

(If you want to confirm that they are really in different packages, just make one of the classes referred to by the controlling classnon-public and try to compile the program.)

In other words, in this sample program, we create our own package structure and populate it with a set of cooperating class files.

A folder named jnk is a child of the root folder on the M-drive.

A folder named SampleCode is a child of the folder named jnk .

A folder named Combined is a child of the folder named SampleCode .

A folder named Java is a child of the folder named Combined .

Folders named p1 and p2 are children of the folder named Java .

The file named Package00.java , shown in Listing 1 is stored in the folder named Java .

Listing 1 . File: Package00.java.
/*File Package00.java Copyright 1997, R.G.Baldwin Illustrates use of package and import directives tobuild an application consisting of classes in three separate packages.The output from running the program follows:Starting Package00 Instantiate obj of public classes in different packagesConstructing Package01 object in folder p1 Constructing Package02 object in folder p2Back in main of Package00 **********************************************************/package Combined.Java; //package directive //Two import directivesimport Combined.Java.p1.Package01;//specific form import Combined.Java.p2.*; //wildcard formclass Package00{ public static void main(String[]args){ //main method System.out.println("Starting Package00");System.out.println("Instantiate obj of public " +"classes in different packages"); new Package01();//Instantiate objects of two classesnew Package02();// in different packages. System.out.println("Back in main of Package00");}//end main method}//End Package00 class definition.

The file named Package01.java , shown in Listing 2 is stored in the folder named p1 .

Listing 2 . File Package01.java.
/*File Package01.java Copyright 1997, R.G.Baldwin See discussion in file Package00.java**********************************************************/ package Combined.Java.p1;public class Package01 { public Package01(){//constructorSystem.out.println( "Constructing Package01 object in folder p1");}//end constructor }//End Package01 class definition.

The file named Package02.java , shown in Listing 3 is stored in the folder named p2 .

Listing 3 . File Package02.java.
/*File Package02.java Copyright 1997, R.G.Baldwin See discussion in file Package00.java**********************************************************/ package Combined.Java.p2;public class Package02 { public Package02(){//constructorSystem.out.println( "Constructing Package02 object in folder p2");}//end constructor }//End Package02 class definition.

The file named CompileAndRun .bat, shown in Listing 4 is stored in the folder named SampleCode .

Listing 4 . File: CompileAndRun.bat.
echo off rem This file is located in folder named M:\SampleCode,rem which is Parent of folder Combined. del Combined\Java\*.classdel Combined\Java\p1\*.class del Combined\Java\p2\*.classjavac -cp M:\jnk\SampleCode Combined\Java\Package00.java java -cp M:\jnk\SampleCode Combined.Java.Package00pause

The controlling class named Package00 is stored in the package named Combined.Java , as declared in Listing 1 .

The class named Package01 is stored in the package named Combined.Java.p1 , as declared in Listing 2 .

The class named Package02 is stored in the package named Combined.Java.p2 , as declared in Listing 3 .

The controlling class named Package00 imports Combined.Java.p1.Package01 and Combined.Java.p2.* , as declared in Listing 1 .

Code in the main method of the controlling class in Listing 1 instantiates objects of the other two classes in different packages. Theconstructors for those two classes announce that they are being constructed.

The two classes being instantiated are public . Otherwise, it would not be possible to instantiate them from outside their respectivepackages.

This program was tested using JDK 7 under Windows by executing the batch file named CompileAndRun.bat .

The classpath is set to the parent folder of the folder named Combined (M:\jnk\SampleCode) by the -cp switch in the file named CompileAndRun.bat .

The output from running the program is shown in the comments at the beginning of Listing 1 .

Run the program

I encourage you to copy the code from Listing1 through Listing 4 into a properly constructed tree of folders. Compile the code and executeit. Experiment with the code, making changes, and observing the results of your changes. Make certain that youcan explain why your changes behave as they do.

Looking ahead

As you approach the end of this group of Programming Fundamentals modules, you should be preparing yourself for the more challenging ITSE 2321 OOPtracks identified below:

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Jb0270: Java OOP: Packages
  • File: Jb0270.htm
  • Originally published: 1997
  • Published at cnx.org: 11/25/12
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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