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Listing 5 . The Comparator.
class TheComparator implements Comparator,Serializable{ public int compare(Object o1,Object o2){if(!(o1 instanceof String)) throw new ClassCastException();if(!(o2 instanceof String)) throw new ClassCastException();int result = ((String)o1).compareTo(((String)o2)); return result*(-1);}//end compare() }//end class TheComparator

I have presented and explained this class in previous modules, so I won't discuss it in detail again here. Suffice it for now to say that an objectinstantiated from this class will induce the list to be sorted into reverse natural order .

Display the sorted list

The code in Listing 6 gets and uses an iterator to display the contents of the sorted list.

Listing 6 . Display the sorted list.
iter = ref.iterator(); while(iter.hasNext()){System.out.print(iter.next() + " "); }//end while loop

The output produced by the code in Listing 6 is shown below:

Tom TOM Joe JOE Bill BILL

As you can see, this is reverse natural order as induced by the Comparator object.

Run the program

I encourage you to copy the code from Listing 1 . Paste the code into your Java editor. Thencompile 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 youcan explain why your changes behave as they do.

Summary

In this module, I taught you how to use the sort method of the Collections class along with a Comparator object to sort the contents of a list.

By using this approach, you can sort the contents of list according to any set of comparison rules that you can program into the compare method of the Comparator object.

Furthermore, the ability to sort the list is independent of the actual implementation of the list, so long as the list properly implements the List interface. For example, the same Comparator object (and the same code) can be used to sort an ArrayList , a LinkedList , or a Vector , producing the same results regardless of which class the list object isinstantiated from.

What's next?

In the next module, I will show you how to use a Comparator created by the reverseOrder method of the Collections class to sort a list into reverse natural order . I will also show you how to use the reverse method of the Collections class to reverse the order of the elements in a list.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4130: The Comparator Interface, Part 5
  • File: Java4130.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

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
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
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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
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
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Adin
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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 did you get the value of 2000N.What calculations are needed to arrive at it
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