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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

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 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
How can I make nanorobot?
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
how can I make nanorobot?
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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