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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

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
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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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