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Optional Collection operations

The following list shows the optional operations in the Collection interface. Each of these methods has the ability to modifythe contents of the collection.

  • add()
  • addAll()
  • clear()
  • remove()
  • removeAll()
  • retainAll()

Optional Map operations

The following list shows the optional operations in the Map interface. Each of these methods also has the ability to modify the contents ofthe map.

  • clear()
  • put()
  • putAll()
  • remove()

Many methods are not optional

In both cases, the interface declares numerous other methods that are not optional. Generally, the non-optional methods don't have the ability tomodify the collection. For example, the get method of the Map interface is not optional. Although the get method receives an incoming key and returns the value to which the key maps, the method doesn't have the ability to modify the contents of the collection.

Run the program

I encourage you to copy the code from Listing 1 and paste it into your Java editor. Thencompile and execute it.

Run the program and observe the results. Experiment with the code. Make changes, run the program again, and observe the results of your changes. Make certain that youcan explain why your changes behave as they do.


A collections framework contains at least the following items:

  • interfaces
  • implementations
  • algorithms

The Java Collections Framework defines eight core interfaces, in two distinct trees. One tree is rooted in Collection and the other is rooted in Map .

The basic purpose of the core interfaces is to make it possible for collections to be manipulated without regard for how they are implemented, solong as the implementation satisfies the contracts of the interfaces.

When the same method name (and signature) is called on references to collections of different types, the behavior of the method is likely to be different for each collection.However, in each case, that behavior will be appropriate for the type of collection object on which the method is called. This is polymorphicbehavior.

Six of the methods declared in the Collection interface are optional insofar as being supported by implementing classes is concerned. The optional methodsall have the ability to modify the contents of the collection. Those implementing classes that don't support an optional method must throw an UnsupportedOperationException if that method is called on an object of the class. Similarly four of the methods declared in the Map interface are optional.

Many methods declared in the Collection interface are not optional. Generally, the non-optional methods don't have the ability to modify thecollection.

What's next?

In the next module, I will discuss and illustrate some of the details of the core interfaces and the general-purpose implementations in the Java CollectionsFramework. For example, I will discuss the difference between a set and a list . I will also discuss the difference between ordered and sorted . I will discuss the fact that additional stipulations are applied as you progressdown the framework interface hierarchy. In order to help you learn and retain the material, I will provide a couple of short quizzes.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Java4050: Core Collection Interfaces
  • File: Java4050.htm
  • Published: 04/18/13

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.


Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
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.
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
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