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Listing 9 . Display the contents of the TreeSet object.
iter = ref.iterator(); while(iter.hasNext()){System.out.print(iter.next()); }//end while loop

The output produced by this code fragment is shown below.

1234

As you can see, the duplicate elements having the value 4 were eliminated as would be expected for a Set object. In addition, the Comparator was used to accomplish the following contract of a SortedSet object:

"A set that further guarantees that its iterator will traverse the set in ascending element order, sorted according to the natural ordering of itselements (see Comparable ), or by a Comparator provided at sorted set creation time."

In this case, the sorted order was controlled by the Comparator object, and not by the natural ordering of the elements. The natural ordering is controlled by implementation of the Comparable interface, and the elements in this collection did not implement the Comparable interface. Therefore, objects of the class named MyClass do not have a natural order in this program.

However, the code in this version of the Comparator produced an output order that matches the ascending natural order that one might expectfor objects of type MyClass . Future modules will show you how to design the Comparator object to produce different output orders, such as descending order for example.

Run the program

I encourage you to copy the code Listing 2 and paste it into your Java 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 youcan explain why your changes behave as they do.

Summary

This module has discussed and illustrated the use of the Comparator interface.

The sorting order established by a Comparator may be different or may be the same as the natural ordering for a collection of objects .

A Comparator can be used to establish a sorting order for objects that don't have a natural ordering .

The use of a Comparator is an alternative to the implementation of the Comparable interface.

A TreeSet object instantiated with the benefit of a Comparator object doesn't require the objects in its collection to implement Comparable .

What's next?

In the next module, I will illustrate the use of a Comparator to eliminate the effect of case when sorting String objects.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4090: The Comparator Interface, Part 1
  • File: Java4090.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 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
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
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
How can I make nanorobot?
Lily
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
how can I make nanorobot?
Lily
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
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