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If you define any constructors, the default constructor will no longer be provided automatically. Therefore, if a constructor that takes no arguments willever be needed for your new class, and you define one or more parameterized constructors, you must define the noarg constructor when you define your class.

A parameterized constructor for Worker

The class named Worker in this program defines a constructor that receives two incoming parameters, one of type int and the other of type boolean . It uses those two incoming parameters to initialize two instance variables of the new object.

Oops!

However, it does not define a constructor with no arguments in the formal argument list (commonly called a noarg constructor) .

Calling the missing noarg constructor

The following code in the main method of the controlling class attempts to instantiate two objects of the Worker class. The first call of the constructor passes no parameters to the constructor. Thus, it requires a noarg constructor in order to instantiate the object.

public class Ap118{ public static void main(String args[]){new Worker().display(); new Worker(5,true).display();System.out.println(); }//end main()}//end class Ap118

A compiler error

Since there is no constructor defined in the Worker class with an empty formal argument list (and the default version is not provided) , the program produces the following compiler error.

Ap118.java:11: cannot resolve symbol symbol : constructor Worker() location: class Workernew Worker().display();

Back to Question 9

Answer 8

C. 0 0.0 false

Explanation 8

All instance variables are initialized to default values

All instance variables are automatically initialized to default values if the author of the class doesn't take explicit steps to cause them to initialized toother values.

The default values

Numeric variables are automatically initialized to zero, while boolean variables are automatically initialized to false. Instance variables of type char are initialized to a Unicode value with all 16 bits set to zero. Reference variables are initialized to null.

Back to Question 8

Answer 7

A. Compiler Error

Explanation 7

Pushing the compiler beyond its limits

Compared to many programming environments, the Java compiler is very forgiving. However, there is a limit to how far even the Java compiler iswilling to go to keep us out of trouble.

Initializing the value of a static variable

We can initialize the value of a static variable using an initialization expression as follows:

public static final MY_CONSTANT = initialization expression;

Important point

It is necessary for the compiler to be able to evaluate the initialization expression when it is encountered.

Illegal forward reference

This program attempts to use an initialization expression that makes use of the value of another static variable (myPI) that has not yet been established at that point in the compilation process. As a result, the program produces thefollowing compiler error under JDK 1.3.

Ap116.java:18: illegal forward reference = 2 * myPI;^

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
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
hey
Giriraj
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
ya I also want to know the raman spectra
Bhagvanji
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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