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Listing 5 . Copy collection elements into an array.
array = (JComponent[])ref.toArray(array);showArray(array,"New array contents");

The code in Listing 5 also causes the contents of the array to be displayed after it receives the elements from the collection.

The first statement in Listing 5 causes the first seven elements in the array to be overwritten with element values from the collection (plus one null value).

The second statement in Listing 5 causes the contents of the array to be displayed.

The toArray method

The most important thing to note about Listing 5 is that a reference to an array object is passed as a parameter to the toArray method. (The simpler version of the toArray method, discussed in the previous module, doesn'ttake any parameters.)

The essential difference

The essential difference between the two overloaded versions of the toArray method has to do with the origin of the array into which the toArray method copies the elements from the collection.

With the simpler version of the toArray method that takes no parameters. The toArray method creates a new array object of type Object , populates it, and returns that object's reference as type Object .

Type is not an issue for the simpler version

Since the new array object is of type Object , (when the rules for Generics are not adhered to) there are no issues regarding type compatibility between the type of the array and the types of theelements stored in the collection. A reference to an object of any type can be stored in an array of the generic type Object[] .

Size is not an issue for the simpler version

Also, since the array is created when it is needed by the simpler version of the toArray method, there are also no size issues. The array is created to be of the correct size to contain copies of all of the elements inthe collection.

More-complex version presents some issues

With the more-complex version of the toArray method (shown in Listing 5 ) , the programmer must provide the array object that will be populated by the toArray method. In this situation, there are size issues as well as type issues to be dealt with.

The type issue

Here is some of what the Oracle documentation for the LinkedList class has to say about the type issue for this version of the toArray method:

"Returns an array containing all of the elements in this list in the correct order. The runtime type of the returned array is that of thespecified array. ... Throws: ArrayStoreException - if the runtime type of (the specified array) is not a supertype of the runtime type of everyelement in this list.

In other words, the type of the array passed as a parameter to the toArray method must be a superclass of the classes from which all of the objects beingmanaged by the collection were instantiated.

Two types of objects in this collection

In this program, the collection is managing objects of the types JButton and JLabel . Each of these types is a subclass of the class named JComponent . For that reason, the type of array that I instantiated and passed to the toArray method is JComponent[] .

Questions & Answers

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
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
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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
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