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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:


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

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.


Questions & Answers

how can chip be made from sand
Eke Reply
is this allso about nanoscale material
are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
where is the latest information on a no technology how can I find it
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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