# 0.2 Learning objects for methods in java  (Page 4/6)

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Exercise Write a recursive method to compute the n'th Fibonacci number:

$fib\left(0\right)=0,fib\left(1\right)=1,fib\left(n\right)=fib\left(n-1\right)+fib\left(n-2\right)\phantom{\rule{0.277778em}{0ex}}\phantom{\rule{0.277778em}{0ex}}\mathit{for}\phantom{\rule{0.277778em}{0ex}}\phantom{\rule{0.277778em}{0ex}}n>1.$

Exercise Write a more efficient nonrecursive method for the same function.

## Calling methods on an object

Concept Nonstatic methods defined in a class must be invoked on an object of the class. A reference to the object becomes an implicit actual parameter that initializes a formal variable called this in the method. The variable this need not be explicitly mentioned when accessing fields of the object unless there is an ambiguity.

Program: Method05.java

// Learning Object Method05 //    calling methods on an objectclass Song {     int seconds;      Song(int s) {        seconds = s;     }      double computePrice(double pricePerSecond) {       return seconds * pricePerSecond;     }}  public class Method05 {     public static void main(/*String[] args*/) {         Song song1 = new Song(164);        Song song2 = new Song(103);         double price1 = song1.computePrice(0.01);        double price2 = song2.computePrice(0.02);         System.out.println(price1);        System.out.println(price2);     }}

This program computes the cost of a song as the product of its length in seconds and the price per second. A class Song is defined to encapsulate the field seconds and the method computePrice .

• Two objects of class Song are instantiated and references to them are assigned to the variables song1 and song2 .
• The method computePrice is called on the object referenced by song1 . In Jeliot this is visualized by an arrow to the object placed in the Expression Evaluation Area followed by a period and the method name and parameters.
• An activation record is allocated containing two formal parameters: this is initialized by the implicit reference and pricePerSecond is initialized from the actual parameter.
• The reference in the parameter this is used to obtain the value of the field seconds . An expression is evaluated and its value returned.
• The activation record is deallocated and the value returned is stored in the variable price1 .
• A second call to the method is executed in exactly the same way, except that it is called on the object referenced by song2 .
• The values of price1 and price2 are printed.

Exercise Modify the method so that the formal parameter is also named seconds . Yes, it can be done! (Hint: read the Concept paragraph above.)

## Calling a method on the same object

Concept A nonstatic method defined in a class that is invoked on an object of the class can invoke another such method on the same object. The object for the second call is the same as the one on the first call,namely, the only referenced by this . There is no need to explicitly write this and the object may be accessed implicitly.

Program: Method06A.java

// Learning Object Method06A //    calling a method on the same objectclass Song {     int seconds;      Song(int s) {        seconds = s;     }      boolean discount(int s) {        return s > 300;     }      double computePrice(double pricePerSecond) {        double price = seconds * pricePerSecond;         if (discount(seconds))            price = price * 0.9;         return price;    } }  public class Method06A {    public static void main(/*String[] args*/) {        Song song1 = new Song(164);         Song song2 = new Song(403);        double price1 = song1.computePrice(0.01);         double price2 = song2.computePrice(0.01);        System.out.println(price1);         System.out.println(price2);    } }

how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Do somebody tell me a best nano engineering book for beginners?
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
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
Uday
I'm interested in Nanotube
Uday
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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