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According to Baldwin, static members can be useful in some situations, but the overuse of static members can lead to problems similar to those experienced in languages that support global variables and global functions.

Revised: Thu Mar 31 15:56:25 CDT 2016

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Table of contents


This module is one of a series of modules designed to teach you about Object-Oriented Programming (OOP) using Java.

Viewing tip

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.


  • Figure 1 . Output date and time.
  • Figure 2 . Five seconds later.
  • Figure 3 . Same date and time as before.
  • Figure 4 . A new date and time.
  • Figure 5 . Same date and time as before.
  • Figure 6 . Output from overridden toString method in Date class.



Static members

There is another aspect of OOP in Java that I have avoided up to this point in the discussion: static variables and static methods.

Tends to complicate ...

I have avoided this topic because, while not particularly difficult, the existence of static members tends to break up the simple structures that I have discussed in previous modules in this collection.

While static members can be useful in some situations, the existence of static members tends to complicate the overall object-oriented structure of Java.

Avoid overuse of static members

Furthermore, the overuse of static members can lead to problems similar to those experienced in languages like C and C++ that support global variables andglobal functions.

When to use static members

I will discuss the use of static members in this module, and will provide some guidelines for their use.

The class named Class

I will also introduce the class named Class and discuss how it enters into the use of static variables and methods.

Instance members versus class members

I will describe the differences between instance members and class members with particular emphasis being placed on their accessibility.

Three kinds of objects

From a conceptual viewpoint, there are at least three kinds of objects involved in a Java program:

  • Ordinary objects
  • Array objects
  • Class objects

Ordinary objects

All (or at least most) of the discussion up to this point in the collection deals with what I have referred to in the above list as ordinary objects .

Questions & Answers

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.
what is biological synthesis of nanoparticles
Sanket Reply
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