<< Chapter < Page Chapter >> Page >

According to The Java Tutorial from Oracle, a collection (sometimes called a container) is also an object that groups multiple elements into a single unit.

Typical collection objects might contain information about employees in the company telephone book, all the purchase orders issued during the past year, orthe transactions occurring in a person's checking account.

Slightly different terminology

Note that this terminology may be somewhat different from what you are accustomed to. For example, if you speak of your coin collection, you are probably speaking about the actual coins rather than the container that holdsthe coins.

This is an important distinction. The usage of the term collection in the Collections Framework usually refers to the container and not to the contents of the container. In the framework, the contents are usually referred to as the elements .

Store references rather than objects

The collections in the framework always store references to objects, rather than storing the objects themselves. One consequence of this is that primitivevalues cannot be stored in a collection without first encapsulating them in an object. (Standard wrapper classes are provided for encapsulating all primitive types.)

Stored as type Object

Furthermore, the references are always stored as type Object . Prior to Java version 1.5, when you retrieved an element from a collection, you frequently needed to downcastit before you could gain access to the members of the object to which the reference refers. Version 1.5 introduced Generics into the Java programming environment, which eliminated that requirement, (provided that you use the more complex syntax required by Generics) .

Moving data among methods

In addition to their use for storing, retrieving, and manipulating data, collections are also used to move data among methods.

One of the primary advantages of the Collections Framework is the ability to pass a collection to a method as the generic interface type Collection . The receiving method doesn't need to know the actual type of the object referredto by the incoming reference in order to call its methods.

Polymorphic behavior

The receiving method can call (on the reference to the Collection object) any of the methods declared in the Collection interface, with confidence that the behavior of the method will be appropriate for the actual type of Collection object involved. (That is polymorphic behavior.)

Core collection interfaces

If you have been working with the framework, you might be inclined to think that all of the interfaces in the following list are members of the core collection interfaces.

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

However, that is not the case.

While the Iterator interface is heavily used in conjunction with collections, according to The Java Tutorial from Oracle, it is not one of the core collection interfaces.

The core collection interfaces identified by the Oracle book are shown below, with indentation showing the parent-child relationships among theinterfaces.

Questions & Answers

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
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
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
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with java' conversation and receive update notifications?