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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

what is the coefficient of -4×
Mehri Reply
-1
Shedrak
the operation * is x * y =x + y/ 1+(x × y) show if the operation is commutative if x × y is not equal to -1
Alfred Reply
An investment account was opened with an initial deposit of $9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
Kala Reply
lim x to infinity e^1-e^-1/log(1+x)
given eccentricity and a point find the equiation
Moses Reply
12, 17, 22.... 25th term
Alexandra Reply
12, 17, 22.... 25th term
Akash
College algebra is really hard?
Shirleen Reply
Absolutely, for me. My problems with math started in First grade...involving a nun Sister Anastasia, bad vision, talking & getting expelled from Catholic school. When it comes to math I just can't focus and all I can hear is our family silverware banging and clanging on the pink Formica table.
Carole
I'm 13 and I understand it great
AJ
I am 1 year old but I can do it! 1+1=2 proof very hard for me though.
Atone
hi
Adu
Not really they are just easy concepts which can be understood if you have great basics. I am 14 I understood them easily.
Vedant
find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
If f(x) = x-2 then, f(3) when 5f(x+1) 5((3-2)+1) 5(1+1) 5(2) 10
Augustine
how do they get the third part x = (32)5/4
kinnecy Reply
make 5/4 into a mixed number, make that a decimal, and then multiply 32 by the decimal 5/4 turns out to be
AJ
how
Sheref
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
hi
Ayuba
Hello
opoku
hi
Ali
greetings from Iran
Ali
salut. from Algeria
Bach
hi
Nharnhar
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Kimberly Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
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
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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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