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

 Page 4 / 6

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);    } }

what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
is it 3×y ?
J, combine like terms 7x-4y
im not good at math so would this help me
how did I we'll learn this
f(x)= 2|x+5| find f(-6)
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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
can nanotechnology change the direction of the face of the world
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.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
Got questions? Join the online conversation and get instant answers!