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A new object of the target class

However, the code in Listing 27 goes beyond that. In particular, the code in Listing 27 creates a new object from which to get the data that is to be plotted.

In some cases, this may be required, depending on the nature of the class from which that object is instantiated. In other cases, it may not be necessary,and could slow down the re-plotting process.

If your class doesn't contain counters or other variables that need to be re-initialized whenever you re-plot, you could probably safely remove or disablethe code in Listing 27 . This will make the program run faster, although you may not be able to see the difference.

The remainder of the event handler

The remaining code in the event handler is shown in Listing 28 .

Listing 28. The remainder of the event handler.
//Set plotting parameters using // data from the text fields.xMin = Double.parseDouble( xMinTxt.getText());xMax = Double.parseDouble( xMaxTxt.getText());yMin = Double.parseDouble( yMinTxt.getText());yMax = Double.parseDouble( yMaxTxt.getText());xTicInt = Double.parseDouble( xTicIntTxt.getText());yTicInt = Double.parseDouble( yTicIntTxt.getText());xCalcInc = Double.parseDouble( xCalcIncTxt.getText());//Calculate new values for the // length of the tic marks on the// axes. If too small on x-axis, // a default value is used later.xTicLen = (yMax-yMin)/50; yTicLen = (xMax-xMin)/50;//Repaint the plotting areas for(int cnt = 0;cnt<number; cnt++){ canvases[cnt].repaint(); }//end for loop}//end actionPerformed

This code is very straightforward. It performs the following actions:

  • Get new plotting parameters from the text fields.
  • Perform some calculations.
  • Cause each of the MyCanvas objects to be repainted using the new plotting parameters.

Again, I will let the comments provide any necessary explanations.

That brings us to the most interesting part of the program, the extended Canvas class.

Beginning of the class named MyCanvas

The class named MyCanvas is an inner class of the GUI class, which is used to override the paint method in each of the plotting areas shown in Figure 1 .

(Virtually all graphics operations in Java, other than those involving standard GUI components, are implemented by overriding the paint method on an object.)

The beginning of this class definition is shown in Listing 29 .

Listing 29. Beginning of the class named MyCanvas.
class MyCanvas extends Canvas{ int cnt;//object number//Factors to convert from double // values to integer pixel locations.double xScale; double yScale;MyCanvas(int cnt){//save obj number this.cnt = cnt;}//end constructor

Floating data vs. pixels

Most of the calculations in this program are performed on data of type double . However, graphics operations are ultimately performed in terms integer numbers of pixels. The code in Listing 29 declares scale factors used later to convert from double values to integer pixel locations.

Questions & Answers

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
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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