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Listing 3 . The Populator class.
class 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

Don't know, don't care

As you can see in the above fragment, the fillIt method receives the reference to the TreeSet object as type Collection . This method doesn't know, and doesn't care, what the actual type of the object is. All itcares about is that the object is a Collection object. (Otherwise, the object's reference couldn't be passed in as a parameter. A type mismatch would occur.)

Because the incoming parameter is a reference to a Collection object, the fillIt method can call the add method on the object with confidence that the behavior of the add method will be appropriate for the specific type of object involved. (For example, the behavior of the add method for an object of the TreeSet class will probably be different from thebehavior of the add method for an object of some other class that implements the Collection interface.)

Polymorphism in action

The great thing about polymorphic behavior is that the author of the fillIt method doesn't need to be concerned about the implementation details of the add method.

Add five elements with some duplicates

The code in the fillIt method adds five elements to the object. Each element is a reference to a new object of type Integer . Two of the objects encapsulate the int value 4, and thus are duplicates.

The int values encapsulated in the Integer objects are not in ascending order. Rather, they are added to the object in descending order. (They could be added in any order and the end result would be the same.)

Filter out the duplicates

The add method for the TreeSet object filters out the duplicate element in order to satisfy the contract of the Collection interface.

Notification of duplicates

In this case, the author didn't care what happens in the case of duplicate elements. If the author of the fillIt method does care what happens in the case of duplicates, she can find out when an object is a duplicate.

According to the contract of the Collection interface, the add method must return true if the call to the method modifies the contents of the object and must return false if the collection does not permit duplicates and the collection already contains the specified element.

Sort the elements

Even though the elements are passed to the add method in descending order (or could be passed in any other order), they are stored and maintained in the TreeSet object in such a way that they can later be accessed in ascending order.

The TreeSet object is now populated

When the fillIt method returns, the TreeSet object contains four (not five) elements with no duplicates. Each element is a reference to an object of type Integer . Those references are maintained in such a way as to make them accessible in ascending order, based on the int values encapsulated in each of the Integer objects.

Get an Iterator object

Returning now to the doIt method in the Worker class that was called in Listing 1 , the statement in Listing 4 calls the iterator method on the TreeSet object's reference that is stored in the reference variable of type Collection .

Questions & Answers

Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
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.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
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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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