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Instantiate and populate an ArrayList object

One of the capabilities of the Collection Framework is to create a new Collection object and populate it with the contents of an existing Collection object of a different (or the same) actual type.

The code in Listing 3 instantiates an ArrayList object and populatesit with the contents of the existing TreeSet object. As a result, we then have two different Collection objects of different actual types containing the same elements.

Listing 3 . Instantiate and populate an ArrayList object.
Collection aList = new ArrayList(aTree);

Identify a target element

The objective of this program is to compare the times required to search for and to find an element in each of the collections. Thus, we need a target elementto search for.

The code in Listing 4 extracts a value near the center of the ArrayList object using an index to find and extract the value. This is a very fast operation on a List object. This value is saved in testVal to be used later for test purposes.

Note that the reference to the ArrayList object was saved as type Collection (and not as type ArrayList ) in Listing 3 above.

Note also that it was necessary to cast that reference to type List in Listing 4 in order to call the get method on the reference. This is because the Collection interface does not declare a method named get . Rather, the get method is added to the List interface to define a more specialized form of collection.

(Author's note: This program was originally written before the introduction of Generics. The above requirement may not be true if the programwere to be rewritten making proper use of Generics.)
Listing 4 . Identify a target element.
Object testVal = ((List)aList).get(size/2);

Search for the test value in each collection

The code in Listing 5 calls the contains method to search for the test value in each of the collections. It uses the system clock to measurethe time required to find the element in each case. (I will assume that you understand how to use the Date class for this purpose, and won't provide a detailed explanation.)

Listing 5 . Search for the test value in each collection.
long start = new Date().getTime(); boolean found = aList.contains(testVal);long stop = new Date().getTime(); System.out.println(found + " " + (stop - start));start = new Date().getTime(); for(int x = 0; x<100000; x++){ found = aTree.contains(testVal);}//end for loop stop = new Date().getTime();System.out.println(found + " " + (stop - start)/100000.0); }//end doIt()

Program output

Running the program several times produced the following range of output values:

  • First output value ranged from "true 93" to "true 109"
  • Second output value ranged from "true 0.00031" to "true 0.00046"

The first output value applies to the ArrayList object, and the second output value applies to the TreeSet object.

As we would expect, the test value was successfully found in both cases; hence the display of true in both cases.

Time required to search the ArrayList collection

The output indicates that approximately 100 milliseconds were required to find the test value in the ArrayList object.

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
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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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