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Answer 5

B. Runtime Error

Explanation 5

ClassCastException

There are some situations involving casting where the compiler cannot identify an erroneous condition that is later identified by the runtime system.This is one of those cases.

This program begins with an array of type double []. Thereference to that array is converted to type Object . Then it is cast to type String []. All of these operations are allowed bythe compiler.

However, at runtime, the runtime system expects to find references to objects of type String in the elements of the array. What it finds instead is values of type double stored in the elements of the array.

As a result, a ClassCastException is thrown. Since it isn't caught and handled by the program, the program terminateswith the following error message showing on the screen.

java.lang.ClassCastException: [D at Worker.doArrays(Ap068.java:17)at Ap068.main(Ap068.java:6)

Back to Question 5

Answer 4

C. 1.0 2.0

Explanation 4

Finally, we got it right

Finally, we managed to get it all together. The program compiles and executes correctly. This program illustrates the assignment of an array object'sreference to a reference variable of type Object , and the casting of that reference of type Object back to the correct array type in order to gain access to the elements in the array.

But don't go away, there is a lot more that you need to know about arrays in Java. We will look at some of those things in the questions that follow.

Back to Question 4

Answer 3

A. Compiler Error

Explanation 3

Must use the correct cast syntax

While it is possible to store an array object's reference in a reference variable of type Object , and later cast it back to an array type to gain access to the elements in the array, you must use the correctsyntax in performing the cast. This is not the correct syntax for performing that cast. It is missing the empty square brackets required to indicate a reference to an array object.

A portion of the compiler error produced by JDK 1.3 is shown below:

Ap066.java:17: inconvertible types found : java.lang.Objectrequired: double double C = (double)B;

Back to Question 3

Answer 2

A. Compiler Error

Explanation 2

Must cast back to an array type

This program illustrates another very important point. Although you can assign an array object's reference to a reference variable of type Object , you cannot gain access to the elements in the array while treating it as type Object . Instead, you must cast it back to an array type before you can gain access to the elements in the array object.

A portion of the compiler error produced by JDK 1.3 is shown below:

Ap065.java:18: array required, but java.lang.Object found B[0]+ " " + B[1]);

Back to Question 2

Answer 1

C. I'm OK

Explanation 1

Assigning array reference to type Object

This program illustrates a very important point. You can assign an array object's reference to an ordinary reference variable of type Object . Note that I didn't say Object[] . The empty square brackets are not required when the type is Object .

Standard containers or collections

Later on, when we study the various containers in the Java class libraries (see the Java Collections Framework) , we will see that they store references to all objects, including array objects, as type Object . Thus, if it were not possible to store a reference to an array object in a reference variable of type Object , it would not be possible to use the standard containers to store references to array objects.

Because it is possible to assign an array object's reference to a variable of type Object , it is also possible to store array object references in containers of type Object .

Back to Question 1

-end-

Questions & Answers

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
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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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