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If the boolean value obtained in the above fragment is true, the code instantiates a new object of the IllegalStateException class , and uses the throw keyword to throw an exception of this type.

Program aborts

The program was not designed to gracefully handle such an exception. Therefore the program aborts, displaying the error message shown earlier.

Don't throw an exception

The code in the next fragment shows that if the boolean value tested above is false, the program will display the text OK and run successfully to completion.

}else{ System.out.println("OK");}//end else }//end doIt()

You may need to run the program several times to see both possibilities.

Back to Question 3

Answer 2

The answer is both of the following:

  • D. OK
  • B. Runtime Error

Explanation 2

One cast is allowable ...

It is allowable, but not necessary, to cast the type of an object's reference toward the root of the inheritance hierarchy.

It is also allowable to cast the type of an object's reference along the inheritance hierarchy toward the actual class from which the object wasinstantiated.

Another cast is not allowable ...

However, (excluding interface type casts) , it is not allowable to cast the type of an object's reference in ways that are not related in asubclass-superclass inheritance sense. For example, you cannot cast the type of an object's reference to the type of a sibling of that object.

Two sibling classes

The code in the following fragment defines two simple classes named MyClassA and MyClassB . By default, each of these classes extends the class named Object . Therefore, neither is a superclass of the other. Rather, they are siblings.

class MyClassA{ public String toString(){return "OK "; }//end test()}//end class MyClassA class MyClassB{public String toString(){ return "OK ";}//end test() }//end class MyClassB

Instantiate one object from each sibling class

The code in the next fragment instantiates one object from each of the above classes, and stores references to those objects in reference variables of typeObject.

Then the code causes the overridden toString method of one of the objects to be called by passing that object's reference to the print method.

void doIt(){ Object ref1 = new MyClassA();Object ref2 = new MyClassB(); System.out.print(ref1);

The code in the above fragment causes the text OK to appear on the screen.

Try to cast to a sibling class type

At this point, the reference variable named ref1 holds a reference to an object of type MyClassA . The reference is being held as type Object .

The statement in the next fragment attempts to cast that reference to type MyClassB , which is a sibling of the class named MyClassA .

MyClassB ref3 = (MyClassB)ref1;

A ClassCastException

The above statement causes a ClassCastException to be thrown, which in turn causes the program to abort. The screen output is shown below:

OK java.lang.ClassCastException:MyClassA at Worker.doIt(Ap152.java:24)at Ap152.main(Ap152.java:14)

(Note that the text OK appeared on the screen before the program aborted and displayed diagnostic information on the screen.)

Questions & Answers

how can chip be made from sand
Eke Reply
are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
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
has a lot of application modern world
Kamaluddeen
yes
narayan
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
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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