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The code in Listing 4 isn't particularly interesting. That code simply throws an exception if either of the references passed to the compare method refer to an object of some type other than String .

The interesting code

The most interesting code is shown in Listing 5 . The first statement in Listing 5 uses the compareTo method of the String class to compare the two objects in an ascending natural ordering sense. The behavior of this method is more formally described as follows:

"Returns: the value 0 if the argument is a string lexicographically equal to this string; a value less than 0 if the argument is a stringlexicographically greater than this string; and a value greater than 0 if the argument is a string lexicographically less than this string."
Listing 5 . The most interesting code.
int result = ((String)o1).compareTo(((String)o2)); return result*(-1);

Converting to reverse natural order

The most interesting line of code in this entire program is the return statement shown in Listing 5 . This line of code changes the sign on the value returned by the compareTo method before returning it as the return value for the compare method.

The effect of changing the sign is to return a value that causes the TreeSet collection to arrange the elements in reverse natural order instead of the normal ascending natural order.

As a result, the use of an iterator to access and display the contents of the collection produces the following output:

Tom TOM Joe JOE Bill BILL

For comparison, if the names were arranged in ascending natural order, the output would be as shown below:

BILL Bill JOE Joe TOM Tom

Run the program

I encourage you to copy the code from Listing 1 and paste it into your Javatext editor. Then compile and execute it.

Run the program and observe the results. Experiment with the code. Make changes, run the program again, and observe the results of your changes. Make certain that you can explain why your changes behave as they do.

Summary

In this module, I taught you how to use a Comparator to cause a TreeSet collection to be sorted in reverse natural order. In other words, the sorting order is the same as the natural order except that the order is descending instead of ascending.

What's next?

In the next module, I will show you how to use a Comparator object to sort the contents of an array.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name:Java4110: The Comparator Interface, Part 3
  • File: Java4110.htm
  • Published: 05/07/13
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

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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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