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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

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.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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 did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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