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Calling the noarg constructor

The code in the makeObj method of the Worker class attempted to instantiate a new object using the following code:

NewClass obj = new NewClass();

Since the class definition didn't contain a definition for a noarg constructor, the following compiler error was produced by JDK 1.3.

Ap093.java:18: cannot resolve symbol symbol : constructor NewClass() location: class NewClassNewClass obj = new NewClass();

Back to Question 4

Answer 3

C. An Object

Explanation 3

We finally got it right!

Did you identify the errors in the previous two programs before looking at the answers?

This program declares the class named NewClass correctly and uses the new operator correctly in conjunction with the default noarg constructor for the NewClass class to create a new instance of the class (an object) .

Making the class public

One of the things that I could do differently would be to make the declaration for the NewClass class public (as shown in the following code fragment) .

public class NewClass{ public String toString(){return "An Object"; }//end toString()}//end NewClass

I am a little lazy

The reason that I didn't declare this class public (and haven't done so throughout this series of modules) is because the source code for all public classes and interfaces must be in separate files. While that is probably a good requirement for large programming projects, it isoverkill for simple little programs like I am presenting in this group of self-assessment modules.

Dealing with multiple files

Therefore, in order to avoid the hassle of having to deal with multiple source code files for every program, I have been using package-private access for class definitions other than the controlling class (the controlling class is declared public) . Although I won't get into the details at this point, when a class is not declared public, it is common to saythat it has package-private access instead of public access.

Back to Question 3

Answer 2

A. Compiler Error

Explanation 2

Java is a case-sensitive language

Java keywords must be written exactly as specified. The keyword class cannot be written as Class , which is the problem with this program.

The inappropriate use of the upper-case C in the word Class caused the following compiler error.

Ap091.java:25: 'class' or 'interface' expected Class NewClass{

The solution to the problem

This problem can be resolved by causing the first character in the keyword class to be a lower-case character as shown in the following code fragment.

class NewClass{ public String toString(){return "An Object"; }//end toString()}//end NewClass

Back to Question 2

Answer 1

A. Compiler Error

Explanation 1

Instantiating an object

There are several ways to instantiate an object in Java:

  • Use the newInstance method of the class named Class .
  • Reconstruct a serialized object using an I/O readObject method.
  • Create an initialized array object such as {1,2,3}.
  • Create a String object from a literal string such as "A String".
  • Use the new operator.

Of all of these, the last two are by far the most common.

What you cannot do!

You cannot instantiate a new object using code like the following code fragment that was extracted from this program.

NewClass obj = NewClass();

This program produces the following compiler error:

Ap090.java:18: cannot resolve symbol symbol : method NewClass ()location: class Worker NewClass obj = NewClass();

The solution to the problem

This problem can be solved by inserting the new operator to the left of the constructor as shown in the following code fragment.

NewClass obj = new NewClass();

Back to Question 1

-end-

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
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Maciej
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Virgil
is Bucky paper clear?
CYNTHIA
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
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what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
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Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
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
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
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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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
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Damian
silver nanoparticles could handle the job?
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not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
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I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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how did you get the value of 2000N.What calculations are needed to arrive at it
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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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