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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.


We will start with a quiz

I am going to begin this module with a quiz just to make sure that you are still awake. Is the following statement Trueor False?

The TreeSet class is a direct implementation of the Collection interface.

The answer is False.

The TreeSet class is not a direct implementation of the Collection interface. Rather, the TreeSet class is a direct implementation of the SortedSet interface. The SortedSet interface extends the Set interface, and the Set interface extends the Collection interface.

The interface hierarchy for the Java Collections Framework is shown below:

  • Collection
    • Set
      • SortedSet
    • List
    • Queue
    • Deque
  • Map
    • SortedMap

As you learned in an earlier module, the Java Collections Framework doesn't have a single root. As shown above, there are two distinct trees in theframework -- The Collection hierarchy and the Map hierarchy.

The root of the Collection hierarchy

The Collection interface is the root of the collection hierarchy. The Java Collections Framework doesn't provide any direct implementations of the Collection interface. All of the implementations of the interfaces in the Collection hierarchy implement one of the sub-interfaces of the Collection interface.

What does Oracle say about this?

Here is what the Oracle documentation has to say on the topic of the Collection interface:

"The SDK does not provide any direct implementations of this interface: it provides implementations of more specific sub-interfaces like Set and List . This interface is typically used to pass collections around and manipulate them wheremaximum generality is desired."

The Oracle documentation also states:

"Bags or multisets (unordered collections that may contain duplicate elements) should implement this interface directly."

What about duplicate elements?

Some implementations of Collection allow duplicate elements, and others do not. Implementations of the List interface (such as ArrayList ) allow duplicate elements. Implements of Set and SortedSet (such as TreeSet ) do not allow duplicate elements. This was illustrated in an earlier module.

A sample program in that earlier module created two collection objects and applied the polymorphic add method to add the same elements to each collection. One of the collection objects was of type ArrayList , and the other collection object was of type TreeSet . The elements added to each collection contained one pair of duplicate elements. The duplicate elementwas automatically excluded from the TreeSet object, but was retained in the ArrayList object.

What is a set?

According to Oracle, a Set is a "collection that contains no duplicate elements ... this interface models the mathematical set abstraction."

An object of type Set is typically used to model collections such as Social Security numbers, where duplicates are not allowed.

What is a list?

Also according to Oracle, a List is "An ordered collection (also known as a sequence). The user of this interface has precise control over where in thelist each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list."

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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