<< Chapter < Page Chapter >> Page >

Not difficult to demonstrate

Although this is not demonstrated by this program, it is easy to modify the program to demonstrate this feature.

A String representation of the array object can be displayed using a System.out.println(array) statement before and after the array is passed to the toArray method.

Array as large as or larger than collection

For the cases where my array contained six, seven, or eight elements, and the collection contained six elements, the String representations of the array object before and after the call to the toArray method were the same. For one case, those String representations were as follows:

[Ljavax.swing.JComponent;@49ba38 [Ljavax.swing.JComponent;@49ba38

In other words, the reference variable named array referred to the same array object before and after the call to the toArray method.

Array smaller than the collection

When I reduced the size of the array to five elements, keeping the size of the collection at six elements, the before and after String representations of the array object were as follows:

[Ljavax.swing.JComponent;@506411 [Ljavax.swing.JComponent;@21807c

In this case, the reference to the array object returned by the toArray method was different from the reference that was passed to the toArray method. In other words, the returned reference referred to a different arrayobject than was referred to by the reference that was passed to the toArray method.

Modify an object

As in the program in the previous module, the code shown in Listing 6 modifies the value of the toolTipText property of the object whose reference is stored in index 0 of the array.

Listing 6 . Modify an object .
((JComponent)array[0]).setToolTipText("XX");showArray(array,"Modified array contents"); showCollection(ref,"Collection contents");

The code in Listing 6 also displays the contents of the array and the contents of the collection after the modification is made.

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

Modified array contents XX B1 L2 B3 B4 L5 null 17Collection contents XX B1 L2 B3 B4 L5

Now for the caution

Note that the value of the toolTipText property of the object referred to by the reference at index 0 of the array, and the same property of the objectreferred to by the reference at index 0 of the collection was overwritten by "XX". (This is true because both references refer to the same object.)

This is the case regardless of which version of the toArray method is used. Therefore, the same cautions discussed in the previous module apply hereas well.

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.


In this module, I taught you how to use the more-complex version of the two overloaded versions of the toArray method, declared in the Collection interface, to copy the elements from a collection into an array of type JComponent .

I discussed issues regarding the type of the array and the type of the objects referred to by the elements in the container. I also discussed issuesregarding the size of the array as compared to the number of elements in the collection.

Finally, I reaffirmed that you need to exercise care when using the elements stored in the array, to avoid corrupting the state of the objects referred to bythe elements in the collection.

What's next?

For now, at least, this module concludes the series of modules on the Java Collections Framework. If I have time later, I will come back and add moremodules to teach you how to use the Map and SortedMap interfaces, and the concrete class implementations of those interfaces.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4160: The toArray Method, Part 2
  • File: Java4160.htm
  • Published: 05/07/13

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

are nano particles real
Missy Reply
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
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..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
has a lot of application modern world
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
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.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Berger describes sociologists as concerned with
Mueller Reply
what is hormones?
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now

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?