Java (or possibly just maths) help please!

[Aoami]

Hey guys,

I've been tasked to write a simple java applet to work out the width of 'golden rectangle' after the user inputs the height.

All the basics are done, but i'm having a problem outputting the results, i'm assuming there is a problem with a way i've coded the forumla.

The maths behind 'Golden Rectangles' is;

Say the height is 1cm, then the width is going to be 1.618cm as it follows the golden ratio (1hi obviously). The formula is 1:1+square root of 5 all divided by 2. explained coherently here

Okay, so my program compiles, but outputs 0.0 whatever I enter. Here is my code:

import java.awt.*;
import javax.swing.*;

public class GoldenRatio extends JApplet {

double doheight;


public void init()
{
String height; // height of the rectangle entered by the user
double doheight; // height int converted to a double


// read in the height of the rectangle from the user
height =
JOptionPane.showInputDialog(
"Enter the height of the rectangle" );

// convert height from tpye String to type Double
doheight = Double.parseDouble( height );
}

public void paint(Graphics g)
{
// draw the results with g.drawString
g.drawRect( 15, 10, 270, 20 );
g.drawString( "The width is " + doheight*(doheight*(Math.sqrt(5)+1)/2), 25, 25 );
}
}

Do i need to import anything else to use math.sqrt?

Thanks in advance!

inb4 olololol n00b etc.

 

[Santa's little helper]

Hello... does it need to be an applet? If not, i got the source for some stuff i did a few weeks ago...

 

[Aoami]

It does need to be an applet unfortunately, wouldn't mind seeing the code anyway though if you think it might be relevant

 

[Aoami]

sorted, do nae worry, i was way off.

 

[Santa's little helper]

package ninjaPackage;

import java.awt.*;
import javax.swing.*;

public class Ninja extends JApplet {

Double calc;
String ninja;
String height; // height of the rectangle entered by the user
Double doheight; // height int converted to a double
public void init()
{



// read in the height of the rectangle from the user
height = JOptionPane.showInputDialog("Enter the height of the rectangle" );

// convert height from tpye String to type Double
doheight = Double.parseDouble( height );

}

public void paint(Graphics g)
{
// draw the results with g.drawString
g.drawRect( 15, 10, 270, 20 );
calc = doheight*(doheight*(Math.sqrt(5)+1)/2);
ninja = "The width is " + calc;


g.drawString(ninja, 25, 25);

}
}

 

[Aoami]

Thanks mate.

Any idea how to parse a double to an int?

tried

'int x Integer.parseInt'

but it doesn't work!

 

[Santa's little helper]

Thanks mate.

Any idea how to parse a double to an int?

tried

'int x Integer.parseInt'

but it doesn't work!

Actually I'm 10 times worse to java than you But I'm a pretty good bug hunter (10 years of programming).

A quick google:

int i;
double ld;

ld = 10.0;
i = ld; /*convert double to int*/

 

[Aoami]

Thanks again, tried a few different methods but can't get anything to work. I think the problem lies in the fact the integers i need are stored and not returned so i'm getting confused.

Will keep cracking on!

 

[Overdriven]

Ao:

Double value;

value = (int)5;

Or something like printf...(int)result;

Had to use it a while back.. Lemme look for code. (or I'll write some).. sec

 

[Aoami]

Basically i need to convert 'calc' and 'doheight' (from your code) into ints, but i can't work out how to do it and i've been googling for hours!

When i tried your method it stated 'lack of precision' as the error.

using other methods such as Double.intValue(x) it says it can't find the variable double.intvalue.

GAH!

edit - the whole aim of this change is to print the actual rectangle, which can't be done using doubles, hence the conversion.

 

[Santa's little helper]

I'm a bit confused - the code above i provided, works perfectly.

 

[Jeremiah]

You should just be able to do "calc.intValue()" and "doheight.intValue()" to convert them into ints.


For example, int x = calc.intValue()... at least, according to the java docs thats all you should need... =)

 

[Aoami]

I'm refering to the double to int conversion bit only.

Can't get that to work using any method.

Where do you put it in?

 

[Aoami]

You should just be able to do "calc.intValue()" and "doheight.intValue()" to convert them into ints.


For example, int x = calc.intValue()... at least, according to the java docs thats all you should need... =)

Aye tried that one, error i got was 'double can not be dereferenced.'

Full code here:

public class GoldenRatio extends JApplet {

double width;
double doheight;
int recwidth;
int recheight;

public void init()
{
String height; // height of the rectangle entered by the user
double doheight; // height int converted to a double
double width;




// read in the height of the rectangle from the user
height =
JOptionPane.showInputDialog(
"Enter the height of the rectangle" );

// convert height from tpye String to type Double
doheight = Double.parseDouble(height);


width = doheight*(Math.sqrt(5)+1)/2;

int recwidth = width.intValue();
int recheight = doheight.intValue();
}


public void paint(Graphics g)
{
// draw the results with g.drawString
g.drawRect( 15, 10, recwidth, recheight );

}
}

 

[Jeremiah]

Are you getting confused between the Double object, and the double primitive type? =)

If you've got a double (lets call it y), you can convert it by doing

int x = new Double.intValue() ;

Looking at your code, you are calling a method on the primitive double, which doesn't have any methods =) So you'll need to convert it back to a Double object before calling intValue() ;

 

[Aoami]

Are you getting confused between the Double object, and the double primitive type? =)

If you've got a double (lets call it y), you can convert it by doing

int x = new Double.intValue() ;

Looking at your code, you are calling a method on the primitive double, which doesn't have any methods =) So you'll need to convert it back to a Double object before calling intValue() ;

No idea what any of that means, but thanks

GOOGLE!

 

[Aoami]

import java.awt.*;
import javax.swing.*;

/**
 * Class GoldenRatio - write a description of the class here
 * 
 * @author (Gareth Sweet gs216) 
 * @version (1)
 */
public class GoldenRatio extends JApplet {

double width;
double doheight;
int recwidth;
int recheight;

public void init()
{
String height; // height of the rectangle entered by the user
double doheight; // height int converted to a double
double width;






// read in the height of the rectangle from the user
height =
JOptionPane.showInputDialog(
"Enter the height of the rectangle" );

// convert height from tpye String to type Double
doheight = Double.parseDouble(height);


width = doheight*(Math.sqrt(5)+1)/2;

double width2 = new Double(width);
double doheight2 = new Double(doheight);


int recwidth = width2.intValue();
int recheight = doheight2.intValue();
}


public void paint(Graphics g)
{
// draw the results with g.drawString
g.drawRect( 15, 10, recwidth, recheight );

}
}

Double still can't be dereferenced

 

[Jeremiah]

Try changing:

double width2 = new Double(width);
double doheight2 = new Double(doheight);

to

Double width2 = new Double(width);
Double doheight2 = new Double(doheight);

 

[Chilly]

its great when the fiddly-ness of a language completely obfuscates whats actually going on. ie two fucking lines of maths.

 

[JingleBells]

its great when the fiddly-ness of a language completely obfuscates whats actually going on. ie two fucking lines of maths.

This is why they added auto-boxing to Java in 1.5

The problem is in these lines:

double width2 = new Double(width);
double doheight2 = new Double(doheight);


int recwidth = width2.intValue();
int recheight = doheight2.intValue();

adding "int" infront of recwidth & recheight makes the local variables in the scope of the init() method, and not change the recwidth & recheight global variables.

Replace that with:

recwidth = (int) width;
recheight = (int) doheight;

You may get a warning about loss of precision.

 

[Overdriven]

@Jingle: Pretty much what I said? But you did it showing code examples

 

[JingleBells]

@Jingle: Pretty much what I said? But you did it showing code examples

Indeed, Aoami might actually look at it with code samples

 

[Aoami]

Thanks for the help guys, was due in thursday night so unfortunately i had to hand it in a bit incomplete. Everythign compiled but didnt work as it should, so i should get some marks at least

At least i know now for future reference

 

[Chilly]

this has been a freddyshouse homework club production.

 

[Milkshake]

Can I suggest "Programming with JAVA" by Holmes as your next purchase?

Oh, and "pimp" to my old Uni project for your basic Swing needs - http://www.macs.hw.ac.uk/guidebook

 

[Chilly]

impressive stuart, 4th hit on google for swing tutorials.

 

[Milkshake]

Aye, I get about 3000 hits a month. Just need to update it a bit when I have time, looks a bit dated :S

 

[Chilly]

stick some casino adverts on there, you'll make a mint.

 

[Milkshake]

It's on a Uni box and is a Uni project, so they'd probably own the rights unless I specifically apply for them. I'd have to look into it...thought it was nice having a site like that WITHOUT adverts.

 

[Chilly]

was a joke (but if you do feel like doing it BETFAIR have a great affiliates team /pimp)