Hello. An app I had to make for calculating sphere`s volume and surface area. The code didn`t give the correct result for volume until I cast converted it`s value by adding (double), but it is a double from the beginning(?!):
public class Sphere
public static void main (String args)
Scanner scan = new Scanner (System.in);
double radius, volume, surfaceArea, val;
System.out.print ("Please enter sphere radius : ");
radius = scan.nextDouble();
volume = (double) 4/3 * Math.PI * Math.pow (radius, 3); // [u]Lack of (double) conversion gave the result of:
// 4/3 = 1 because of automatic integer conversion? and not 1.333333333333333[/u]
surfaceArea = 4 * Math.PI * Math.pow (radius, 2);
val = 4/3; [u]//example of result in a double value converted to integer[/u]
DecimalFormat fmt = new DecimalFormat ("0.####");
System.out.println ("Sphere volume : " + fmt.format(volume));
System.out.println ("Sphere surface area : " + fmt.format(surfaceArea));
System.out.println ("4/3 = : " + val); [u]//example of result in a double value converted to integer - Printed[/u]
// result of val = 4/3; is 1, not 1.333333333333333 but it`s a double.
Can someone explain please.
Last replyBest Answer
More aboutbeginner java arithmetics math
I think you have answered your own question in your comments. 4 / 3 = 1, as both are integers. (double) 4 is a double, so (double) 4 / 3 = 1.3333....
You would get the same result by using 4.0 / 3 or 4.0 / 3.0.
Yes it gave the same result with 4.0 (and so 3 converted by promotion to 3.0 too). I thought it`s the variable type that counts.