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Baldwin teaches you about assignment compatibility, type conversion, and casting for both primitive and reference types. He also teaches you about the relationship between reference types, method calls, and the location in the class hierarchy where a method is defined.

Revised: Thu Mar 31 11:49:25 CDT 2016

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Preface

This module is one of a series of modules designed to teach you about the essence of Object-Oriented Programming (OOP) using Java.

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This module discusses type conversion for both primitive and reference types.

A value of a particular type may be assignment compatible with variables of other types, in which case the value can be assigned directly to the variable. Otherwise, it may be possible to perform a cast on the value to change its type and assign it to the variable as the new type.

With regard to reference types, whether or not a cast can be successfully performed

  • depends on the relationships of the classes involved in the class hierarchy.

A reference to any object can be assigned to a reference variable of the type Object , because the Object class is a superclass of every other class.

When we cast a reference along the class hierarchy in a direction from the root class Object toward the leaves, we often refer to it as a downcast .

Whether or not a method can be called on a reference to an object depends on

  • the current type of the reference, and
  • the location in the class hierarchy where the method is defined.

In order to use a reference of a class type to call a method, the method must be defined at or above that class in the class hierarchy.

A sample program is provided that illustrates much of the detail involved in type conversion, method calls, and casting with respect to reference types.

Discussion and sample code

What is polymorphism?

As a quick review, the meaning of the word polymorphism is something like one name, many forms .

How does Java implement polymorphism?

Polymorphism manifests itself in Java in the form of multiple methods having the same name.

In some cases, multiple methods have the same name, but different formal argument lists (overloaded methods, which were discussed in a previous module) .

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 ?
s.
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.
Harper
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
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Cied
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what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
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Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
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
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
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I'm interested in Nanotube
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this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
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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