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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

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 ?
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
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.
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
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
what is system testing
what is the application of nanotechnology?
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
anybody can imagine what will be happen after 100 years from now in nano tech world
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
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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