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Generics

The code in this series of modules is written with no thought given to Generics . As a result, if you copy and compile the code, you will probably get warnings about unchecked or unsafe operations .

While you will ultimately need to understand how to use Generics, that is a very complex topic. An understanding of Generics is beyond the scope of thiscourse. Therefore, for purposes of this course, you can simply ignore those warnings.

Discussion and sample code

Illustration of core collection interfaces

We will begin this module with a little quiz. Take a look at the program shown in Listing 1 and see if you can answer the following question.

What output does the program in Listing 1 produce?

  • A. Compiler Error
  • B. Runtime Error
  • C. 44321 44321
  • D. 12344 12344
  • E. 1234 44321
  • F. 1234 4321
  • D. None of the above.
Listing 1 . The program named Ap401.
import java.util.TreeSet; import java.util.ArrayList;import java.util.Collection; import java.util.Iterator;public class Ap401{ public static void main(String args[]){ new Worker().doIt();}//end main() }//end class Ap401class Worker{ public void doIt(){Collection ref = new TreeSet(); Populator.fillIt(ref);Iterator iter = ref.iterator(); while(iter.hasNext()){System.out.print(iter.next()); }//end while loopSystem.out.print(" "); ref = new ArrayList();Populator.fillIt(ref); iter = ref.iterator();while(iter.hasNext()){ System.out.print(iter.next());}//end while loop System.out.println();}//end doIt() }// end class Workerclass Populator{ public static void fillIt(Collection ref){ref.add(new Integer(4)); ref.add(new Integer(4));ref.add(new Integer(3)); ref.add(new Integer(2));ref.add(new Integer(1)); }//end fillIt()}//end class populator

If you selected the following answer, then you are correct.

E. 1234 44321

The program in Listing 1 illustrates the basic purpose of the core collection interfaces in the Java Collections Framework. That purposeis to allow collections to be manipulated without regard for how the collections are implemented.

Multiple list implementations

For example, there is more than one way to implement a list. Two common ways involve arrays and linked structures. If two lists are implemented indifferent ways, but both satisfy the requirements of the core collection interfaces, they can each be manipulated the same way regardless of the detailsof their implementation.

TreeSet and ArrayList

A collection of type TreeSet and a collection of type ArrayList are instantiated in the program in Listing 1 . Each of the collections is viewed as being of the interface type Collection . A method named add is used to populate each collection with the same values in the same order.

Behavior is different but appropriate

The behavior of the add method is appropriate, and different in each of the two cases, with the final contents of each collection being determined bythe respective behavior of the add method for that type of collection.

The fillIt method

The code in the fragment shown in Listing 2 defines a static method named fillIt of the class named Populator . This is a class of my own design intended solely to illustrate the primary point of this program.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
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
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
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
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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
Do you know which machine is used to that process?
s.
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Berger describes sociologists as concerned with
Mueller 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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