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Listing 4 . Get an Iterator object.
Iterator iter = ref.iterator();

The call to the iterator method on any Collection object returns an instance of a class that implements the Iterator interface. The Iterator object can be used to traverse the collection, gaining access to each element in order. (The concept of in order means different things for different kinds of collections. For a collection instantiated fromthe TreeSet class, in order means in ascending order.)

Again, don't know, don't care

Again, the author of the method that uses the Collection object doesn't need to know or care about the internal implementation of thecollection, or the implementation of the methods of the Iterator object. They simply do what they do, and can be used for their intended purpose.

An Iterator object acts as a doorkeeper

The Iterator interface declares three methods:

  • hasNext()
  • next()
  • remove()

You might say that an Iterator object acts as a doorkeeper for the collection object that it represents, providing access to the contents of thecollection in a very specific manner.

Traverse the collection

The code fragment in Listing 5 below shows how the first two of the above methods can be used to

  • Traverse the collection, accessing each of the object's elements in succession.
  • Display the value encapsulated in the object referred to by each element.

As mentioned earlier, when the collection is an object instantiated from the TreeSet class, access to the elements is provided in ascending order.

Listing 5 . Traverse the collection.
while(iter.hasNext()){ System.out.print(iter.next());}//end while loop

Four elements with no duplicates

At this point, the TreeSet object contains four elements, with no duplicates. Each of the elements is a reference to an object of type Integer . The code in the loop in Listing 5 causes each of those elements to be accessed and displayed in ascending order. This causes the following text to appear on thescreen:


An editorial opinion

In my opinion, this is the kind of knowledge that a computer science student in a modern data structures course should be learning. This is a far departurefrom courses of the past where CS2 students were required to memorize the intricate details of how to implement various data structures.

What kind of knowledge is needed?

Does an architect need to understand the detailed inner workings of an air conditioning compressor to design a cooling system into a building? Ofcourse not!

However, the architect does need to know the tradeoffs among the available cooling systems in terms of initial cost, operating cost, size, efficiency, etc.

Does an audio technician need to understand the detailed inner workings of an electronic audio equalizer in order to construct an integrated audio system?Absolutely not! If that were a requirement, there would likely be very few audio systems in existence.

However, the audio technician does need to understand the tradeoffs among the various available audio equalizers.

The same concept applies to software design

Does an OOP software designer need to know the detailed inner workings of the various kinds of collection objects in order to use them effectively? No!

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
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
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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