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  • Suzie Smith
  • Suzie Jones,
  • Suzie Smith-Jones,
  • Suzie Jones-Smith, or
  • something entirely different.

In this case, there would be a need to modify the object that represents Suziein order to reflect her newly-elected surname. (Or perhaps Tom Jones might elect to thereafter be known as Tom Jones-Smith, in which case it would be necessary to modify the object that represents him.)

An updated telephone book

The person charged with maintaining the database could

  • use the name-changing operation to modify the object and change the name,
  • make use of the sorting operation to re-sort the set of objects, and
  • print and distribute an updated version of the telephone book.

Many user-defined types already exist

Unlike the primitive types which are predefined in the core language, I am unable to give you much in the way of specific information about user-defined types, simply because they don't exist until a user defines them.

I can tell you, however, that when you obtain the Java programming tools from Sun, you not only receive the core language containing the primitive types, you also receive a large library containing several thousand user-defined types that have already been defined. A large documentation package is available from Sun to help you determine the individual characteristics of these user-defined types.

The most important thing

At this stage in your development as a Java programmer, the most important thing for you to know about user-defined types is that they are possible.

You can define new types. Unlike earlier procedural programming languages such as C and Pascal, you are no longer forced to adapt your problem to the available tools. Rather, you now have the opportunity to extend the tools to make them better suited to solve your problem.

The class definition

The specific mechanism that makes it possible for you to define new types in Java is a mechanism known as the class definition .

In Java, whenever you define a new class, you are at the same time defining a new type. Your new type can be as simple, or as complex and powerful as you want it to be.

An object (instance) of your new type can contain a very small amount of data, or it can contain a very large amount of data. The operations that you allow to be performed on an object of your new type can be rudimentary, or they can be very powerful.

It is all up to you

Whenever you define a new class (type) you not only have the opportunity to define the data definition and the operations, you also have a responsibility to do so.

Much to learn and much to do

But, you still have much to learn and much to do before you will need to define new types.

There are a lot of fundamental programming concepts that we will need to cover before we seriously embark on a study involving the definition of new types.

For the present then, simply remember that such a capability is available, and if you work to expand your knowledge of Java programming one small step at a time, when we reach the point of defining new types, you will be ready and eager to do so.

Sample program

I'm not going to provide a sample program in this module. Instead, I will be using what you have learned about Java data types in the sampleprograms in future modules.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Jb0150: Java OOP: A Gentle Introduction to Java Data Types
  • File: Jb0150.htm
  • Published: 11/17/12

Financial : Although the Connexions site makes it possible for you to download a PDFfile for this module at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should be aware thatsome 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.comshowing me as the author. I neither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, pleasebe aware that it is a copy of a module that is freely available on cnx.org and that it was made and published without my prior knowledge.

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


Questions & Answers

how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
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
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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