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Listing 5 creates a URL object that points to the file named page1.html in the directory named baldwin on the server at Austin Community College where I teach.

No port was specified

The URL object will not contain a port specification because I didn't provide a port number. Later when we use one of the methods of the URL class along withthis URL object to make a connection to the server, the connection will, by default, be made to port 80 which is the standard port for servers that support the HTTPprotocol.

In other words, when the port is not provided (the URL object contains a port number of -1) , the connection method of the URL class will use the protocol portion of the URL to decide which port to connect to.

Open a connection to the URL

Once you have a URL object, there are a number of things that you can do with it. One of the things you can do with it is to open input and output streams that will be connected to the server software that is monitoring the port ofinterest.

The code in Listing 6 opens a connection to the URL described by this URL object and returns an input stream object for reading data from the connection. This is the point where the port number defaults on the basis of theprotocol specification in the URL object.

Listing 6 - Open a connection to the URL.
BufferedReader htmlPage = new BufferedReader(new InputStreamReader(url.openStream()));

Be aware that only a small portion of the statement in Listing 6 has to do with URL processing. The remainder of the statement has to do with the more complex topicof I/O stream processing.

Read and display the data

The remaining code in this program, as shown in Listing 7 , is completely straightforward. Data is read from the stream one line at a time and displayedas it is read. The readLine method returns null when there is no more data to be read from the stream and the program terminates.

Listing 7 - Read and display the data.
while((dataLine = htmlPage.readLine()) != null){ System.out.println(dataLine);}//end while loop

Not complicated at all

As you can see, it is very easy to write a program that will connect to an HTTP server and download the contents of a specified file. There are lotsof things that you do by using this as a starting point. A common assignments given tostudents is to add a little more knowledge and code to this and to write a crawler that will crawl the web searching for some specified filecontents.

Run the programs

I encourage you to copy the code from Listing 8 and Listing 9 .Compile the code and execute it. Experiment with the code,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.

What's next?

The next module in the series will deal with the URLConnection class.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4640: The URL Class and the URLEncoder Class
  • File: Java4640.htm
  • Published: 03/02/14
  • Revised: 02/07/16
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.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
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..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
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.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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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