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Ranch Hand
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I am learning how to create classes, and I had to create a class with a program to test it that finds the volume and surface area of a sphere, cylinder, and cone.
I am having some problems- for my cone Volume, it is returning everything as 0. For the program, I have
counter = 1;

System.out.println("Cone Volume");

while (counter <= 10)
{
double radius = Math.random();
System.out.println("Radius: " + radius);
double h = Math.random();
System.out.println("H: " + h);
double coneVolume = yourTurnClass.coneVolume(radius,h);
System.out.println("answer: " + coneVolume);
counter++;
}

________

For the class I have:

public static double coneVolume(double radius, double h)
{

answer = (1/3*((Math.PI)*((radius*radius)*(h))));

return answer;
}

_________

Am I messing something up with pi?

Another problem I have is with coneSurface- I have formula:

public static double coneSurface(double radius, double h)
{

answer = (Math.PI*(radius*(Math.sqrt(h*h + radius*radius) + radius*radius)));
return answer;
}

and program

while (counter <= 10)
{
double radius = Math.random();
System.out.println("Radius: " + radius);
double h = Math.random();
System.out.println("H: " + h);
double coneSurface = yourTurnClass.coneSurface(radius,h);
System.out.println("answer: " + coneSurface);
counter++;
}

and my answers are coming out a bit off. Did I miss my formula up, or call something wrong?

My final problem is with the sphere volume- I have class

public static double sphereVolume(double radius)
{

answer = ((4/3)*(Math.PI)*(radius*radius*radius));
return answer;

}


and program

while (counter <= 10)
{
double radius = Math.random();
System.out.println("Radius: " + radius);
double sphereVolume = yourTurnClass.sphereVolume(radius);
System.out.println("answer: " + sphereVolume);
counter++;
}

_______

with answers slightly wrong again. Is there something I am doing wrong that is the same with all three of these?


THANK YOU SO MUCH FOR YOUR HELP!!!
 
Bartender
Posts: 1812
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Eclipse IDE Java Windows
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Did you look at the API for Math.random()?

It generates a double between 0 and 1. Most people multiply it by a number (say 10) to get a random number (say 0 through 10).

Your problems might stem from the numbers being too small to calculate a valid volume, surface, etc....

Just a thought...
 
Sheriff
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Therese, please Use Code Tags.
 
lowercase baba
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the problem is here: answer = (1/3*((Math.PI)*((radius*radius)*(h))));

your '1' is an int literal. your '3' is an int literal. when you have an int divided by an int, the result is...an int. 1 / 3 = 0 in integer division.

Try changing it to "answer = (1.0/3*((Math.PI)*((radius*radius)*(h))));


update: I see that same issue with your "4/3" as well...
 
Janeice DelVecchio
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It's almost like Java failed out of elementary division. LOL
 
Marshal
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Janeice DelVecchio wrote:It's almost like Java failed out of elementary division. LOL
No, it was given elementary division and stayed with what it was familiar with
 
fred rosenberger
lowercase baba
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There are plenty of times when you WANT the integer division. when combined with the modulus operator, you can do some cool stuff.
 
It is sorta covered in the JavaRanch Style Guide.
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