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Take a preliminary look at the complexity of OOP by examining some aspects of the System and PrintStream classes.

Revised: Mon Mar 28 11:44:44 CDT 2016

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Preface

This module takes a preliminary look at the complexity of OOP by examining some aspects of the System and PrintStream classes.

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Listings

Introduction

This lesson introduces you to the use of the System and PrintStream classes in Java. This is our first introduction to the complexity that can accompany the OOP paradigm. It gets a little complicated, so you might need to pay special attention to the discussion.

Discussion

What does the main method do?

The main method in the controlling class of a Java application controls the flow of the program.

The main method can also access other classes along with the variables and methods of those classes and of objects instantiated from thoseclasses.

The hello1 Application

Listing 1 shows a simple Java application named hello1 .

(By convention, class definitions should begin with an upper-case character. However, the original version of this module was written andpublished in 1997, before that convention was firmly established.)

Listing 1 . The program named hello1.
/*File hello1.java Copyright 1997, R.G.Baldwin **********************************************************/class hello1 { //define the controlling class //define main methodpublic static void main(String[] args){//display text string System.out.println("Hello World");}//end main }//End hello1 class. No semicolon at end of Java class.

Does this program Instantiate objects?

This is a simple example that does not instantiate objects of any other class.

Does this program access another class?

However, it does access another class. It accesses the System class that is provided with the Java development kit. (The System class will be discussed in more detail in a future module.)

The variable named out

The variable named out , referred to in Listing 1 as System.out , is a class variable of the System class. (A class variable is a variable that is declared to be static.)

Recall that a class variable can be accessed without a requirement to instantiate an object of the class. As is the case with all variables, the classvariable must be of some specific type.

Primitive variables vs. reference variables

A class variable may be a primitive variable , which contains a primitive value, or it may be a reference variable , which contains a reference to an object.

(I'll have more to say about the difference between primitive variables andreference variables in a future module.)

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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