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Making the objects distinguishable

After the code in Listing 3 has been executed, the buttons and labels are indistinguishable on the basis of the null value of their toolTipText property.

The code in Listing 4 deals with this issue. This code uses the setToolTipText method to store a unique String value in the toolTipText property of the object referred to by each of the elements in the collection.

Listing 4 . Making the objects distinguishable.
Iterator iter = ref.iterator(); int cnt = 0;JComponent refVar; while(iter.hasNext()){refVar = (JComponent)iter.next(); if(refVar instanceof JButton){refVar.setToolTipText("B"+cnt++); }else{refVar.setToolTipText("L" + cnt++); }//end else}//end while loop }//end fillIt()

Identifying the buttons and labels

In addition to storing a unique value in the toolTipText property of the object referred to by each element, the code in Listing 4 also makes it possible to distinguish between the JButton objects and the JLabel objects. This is accomplished by including an upper-case "B" in the propertyvalue for each JButton , and including an upper-case "L" in the property value for each JLabel button.

Why populate this way?

This approach to population is, admittedly, a little bit of an overkill for illustrating what I want to illustrate in this program. However, I plan to usethe same fillIt method in the sample program in the next module, and it won't be an overkill there.

Display the collection

The code in Listing 2 above calls the showCollection method to display the contents of the populated LinkedList collection. The showCollection method is shown in Listing 5

Listing 5 . The showCollection method.
void showCollection(Collection ref){ Iterator iter = ref.iterator();while(iter.hasNext()){ System.out.print(((JComponent)iter.next()).getToolTipText() + " "); }//end while loopSystem.out.println(); }//end showCollection

By now, you should have no difficulty understanding the code in Listing 5 . This code gets an iterator on the incoming reference of type Collection . The code then uses that iterator to gain access to each element in succession,displaying the String value of the toolTipText property belonging to a particular object during each iteration.

Downcast is required

Note that the next method of the Iterator interface returns a reference to the next element in the collection, as type Object . (Remember, Generics were not used to populate this collection.)

In order to call the getToolTipText method on the returned reference, the reference must be downcast to type JComponent . Since both JButton and JLabel extend JComponent , and the getToolTipText method is declared in the JComponent class, it is not necessary to be concerned as to whether an object is type JButton or type JLabel to display the value of the toolTipText property. (This is an example of polymorphic behavior based on class inheritance.)

The output for the collection

The output produced by the code in Listing 2 is shown below:

Collection contentsB0 B1 L2 B3 B4 L5

By examining the "B" and "L" characters in this output, you can identify the JButton objects and the JLabel objects.

Questions & Answers

how does Neisseria cause meningitis
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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
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Ziyad Reply
How bacteria create energy to survive?
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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
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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
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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
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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
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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 ❣️
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Innocent
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en français
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ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
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skin
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skin,Oral,Nasal,GIt
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all
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by fussion
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part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
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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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