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Answer 1


Explanation 1

Type conversion

This program illustrates type conversion up the inheritance hierarchy, both with and without a cast.

Store object's reference as type Object

The following fragment instantiates a new object of the class named MyClassA , and stores that object's reference in a reference variable of type Object . This demonstrates that you can store an object's reference in a reference variablewhose type is a superclass of the class from which the object was instantiated, with no cast required.

class Worker{ void doIt(){Object refA = new MyClassA();

Cast object's reference to type Object

The code in the next fragment instantiates an object of the class named MyClassB , and stores the object's reference in a reference variable of type Object , after first casting the reference to type Object . This, and the previous fragment demonstrate that while it is allowable to cast a reference to thesuperclass type before storing it in a superclass reference variable, such a cast is not required.

Object refB = (Object)(new MyClassB());

Type conversion and assignment compatibility

This is part of a larger overall topic commonly referred to as type conversion. It also touches the fringes of something that is commonly referredto as assignment-compatibility.

Automatic type conversions

Some kinds of type conversions happen automatically. For example, you can assign a value of type byte to a variable of type int and the type conversion will take place automatically.

Cast is required for narrowing conversions

However, if you attempt to assign a value of type int to a variable of type byte , the assignment will not take place automatically. Rather, the compiler requires you to provide a cast to confirm that you accept responsibility for theconversion, which in the case of int to byte could result in the corruption of data.

Automatic conversions up the inheritance hierarchy

When working with objects, type conversion takes place automatically for conversions toward the root of the inheritance hierarchy.Therefore, conversion from any class type to type Object happen automatically. However, conversions in the direction away from the root require a cast.

(Conversion from any class type to any superclass of that class also happens automatically.)

Polymorphic behavior

The code in the next fragment uses polymorphic behavior to display the contents of the two String objects.

System.out.print(refA); System.out.print(refB);

No cast required

This works without the use of a cast because the print method calls the toString method on any object's reference that it receives as an incoming parameter. The toString method is defined in the Object class, and overridden in the String class. Polymorphic behavior dictates that in such a situation, the version of the method belonging to the object will be called regardless of thetype of the reference variable holding the reference to the object.

When would a cast be required?

Had the program attempted to call a method on the reference that is not defined in the Object , class, it would have been necessary to cast the reference down the inheritance hierarchy in order to successfully call the method.

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Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
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
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