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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

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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