how to use math.pi in java

Question

I am having problems converting this formula V = 4/3 π r^3. I used Math.PI and Math.pow, but I get this error:

';' expected

Also, the diameter variable doesn't work. Is there an error there?

import java.util.Scanner;

import javax.swing.JOptionPane;

public class NumericTypes    
{
    public static void main (String [] args)
    {
        double radius;
        double volume;
        double diameter;

        diameter = JOptionPane.showInputDialog("enter the diameter of a sphere.");

        radius = diameter / 2;

        volume = (4 / 3) Math.PI * Math.pow(radius, 3);

        JOptionPane.showMessageDialog("The radius for the sphere is "+ radius
+ "and the volume of the sphere is ");
    }
}

The next problem you'll encounter is answered here: http://stackoverflow.com/questions/10455677/division-in-java — Greg Hewgill, Sep 26 '12 at 03:14

score 54 · Answer 1 · answered Sep 26 '12 at 03:13

54

You're missing the multiplication operator. Also, you want to do 4/3 in floating point, not integer math.

volume = (4.0 / 3) * Math.PI * Math.pow(radius, 3);
           ^^      ^

answered Sep 26 '12 at 03:13

David Yaw

25,725
4
59
90

score 5 · Answer 2 · edited Oct 20 '17 at 21:55

5

Replace

volume = (4 / 3) Math.PI * Math.pow(radius, 3);

With:

volume = (4 * Math.PI * Math.pow(radius, 3)) / 3;

edited Oct 20 '17 at 21:55

Daniel Trugman

6,100
14
35

answered Oct 20 '17 at 19:17

user3394530

51
1
2

7

Perhaps add some explanation on what you did here? – orhtej2 Oct 20 '17 at 19:25
@orhtej2 (4 / 3) returns 1. So he multiplies with 4 a float in order to get a float and then divides with 3, in order to get a float result. – milia Jan 15 '21 at 14:33

score 4 · Answer 3 · edited Feb 19 '16 at 07:43

Here is usage of Math.PI to find circumference of circle and Area First we take Radius as a string in Message Box and convert it into integer

public class circle {

    public static void main(String[] args) {
        // TODO code application logic here

        String rad;

        float radius,area,circum;

       rad = JOptionPane.showInputDialog("Enter the Radius of circle:");

        radius = Integer.parseInt(rad);
        area = (float) (Math.PI*radius*radius);
        circum = (float) (2*Math.PI*radius);

        JOptionPane.showMessageDialog(null, "Area: " + area,"AREA",JOptionPane.INFORMATION_MESSAGE);
        JOptionPane.showMessageDialog(null, "circumference: " + circum, "Circumfernce",JOptionPane.INFORMATION_MESSAGE);
    }

}

score 1 · Answer 4 · edited Sep 08 '19 at 08:26

1

Your diameter variable won't work because you're trying to store a String into a variable that will only accept a double. In order for it to work you will need to parse it

Ex:

diameter = Double.parseDouble(JOptionPane.showInputDialog("enter the diameter of a sphere.");

edited Sep 08 '19 at 08:26

HK boy

1,380
11
16
21

answered Oct 24 '13 at 06:49

Mark

19
1

how to use math.pi in java

4 Answers4

Linked