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Casting errors are likely

This is a scenario where the programmer is likely to make a casting error when casting elements retrieved from the collection. Unless the programmeruses the instanceof operator to determine the type of a retrieved reference prior to performing the cast, the programmer is depending on hismemory to know the type of each reference in the population on the basis of the index of the element. If the programmer loses track of the types of thedifferent references with respect to the element's indices, a casting error is a strong possibility.

The error scenario

This is the error scenario depicted by the first call to the println method in Listing 6 . In this case, the element at index 0 is a reference to a Date object, and the element at index 1 is a reference to a String object. However, the programmer mistakenly retrieves the element at index 1 and attempts to castit to type Date , which is the type of the reference at index 0. This results in the runtime exception shown in Figure 3 .

Of course, it has always been possible to use the instanceof operator to confirm the type of a reference before performing a cast as a way to avoidthis type of programming error. Good programming practice would dictate the use of that construct when working with references to objects of mixed typesin a single collection.

Dealing with angle brackets in cnxml body text

You are reading this module at cnx.org. Documents published at cnx.org are maintained in a special flavor of xml know as cnxml. Without getting into thedetails, I will tell you that creating cnxml is not an easy task. In order to avoid having to write these modules in raw cnxml code, I originally write themusing a WYSIWYG xhtml editor and then run the xhtml files through a program of my own design that transforms the xhtml document into cnxml.

Unfortunately, my transform program is incapable of handling angle brackets in the body text of the document. Therefore, whenever thebody text in this document needs a left angle bracket, I will indicate the existence of a left or right angle bracket using a text description of the anglebracket. The code in the listings,however, will show the left and right angle brackets intact as required.

Avoiding the requirement to cast through the use of generics

The program named Generics03 shown in Listing 7 illustrates how generics can be used to avoid the requirement to cast references when they are retrieved from acollection.

(While casting is not difficult, avoiding the requirement to cast can also avoid the possibility of casting incorrectly.)

As in the previous programs, the main method in this program instantiates an object of the class named Generics03 and calls the method named runIt on the object.

Instantiate an ArrayList object

Also, as in the previous programs, this program declares an instance variable named var1 and initializes that variable with a reference to a new objectof type ArrayList . However, the syntax that is used for this purpose in this program is significantly different from the syntax used for thesame purpose in the previous two programs.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
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
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
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.
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
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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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