<< Chapter < Page Chapter >> Page >
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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with java' conversation and receive update notifications?

Ask