<< 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

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
Do somebody tell me a best nano engineering book for beginners?
s. Reply
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?
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.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.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?