Average incorrect : decimal point always .0

Question

I'm pretty new to arrays and am trying to create a simple program that calculates the average of 5 numbers. However, when the average is calculated, it always has a decimal point of 0 rather than what it should be, but I'm not sure why.. For example, if I type in 4, 4, 4, 4, 3, it displays 3.0 as the average rather than 3.8. Please help!

        int[] boxes = new int[5];

        for (int i = 1 ; i <= 5 ; i++)
        {
            System.out.print("Enter number " + i + " > ");
            int n = Integer.parseInt(kb.nextLine());

            boxes[i-1] = n;
        }

        double mean = ( boxes[0] + boxes[1] + boxes[2] + boxes[3] + boxes[4] ) / 5;

        System.out.println("The average of those five numbers is: " + mean);

Thank you!! :)

Why do you use `int n = Integer.parseInt(kb.nextLine());` instead of `int n=kb.nextInt();` it's very simple — Mourad BENKDOUR, Nov 21 '15 at 20:46

score 1 · Answer 1 · answered Nov 21 '15 at 20:13

1

it is because the operation is done with integers , change your 5 to 5.0

answered Nov 21 '15 at 20:13

Stéphane

867
4
7

hehe, you've beaten me by a few seconds :-) – collapsar Nov 21 '15 at 20:14
Thank you! That makes sense – Karen Sarmiento Nov 21 '15 at 20:25

score 0 · Answer 2 · answered Nov 21 '15 at 20:19

0

I cannot answer you the specifics but there is a huge topic in java called type casting. I reckon, you read it. This is a good puzzle for you to solve yourself. Reminds me of my past :)

answered Nov 21 '15 at 20:19

KameshG

43
8

Thanks, Ill look into it :) – Karen Sarmiento Nov 21 '15 at 20:26

score 0 · Answer 3 · answered Nov 21 '15 at 20:29

Fast fix: change 5 -> 5.0D.

Why? Let's look at dividing process more detail:

You get sum from all numbers: ( boxes[0] + boxes[1] + boxes[2] + boxes[3] + boxes[4] ), result -> int.
You divide sum(int type) / 5(int type) = result also int type 3.8 -> 3.
Last one its autocast int -> double.

That's why you get what you see.

score 0 · Answer 4 · answered Nov 21 '15 at 21:03

Solution 1 : - You can use 5.0 instead of 5 to have a double division.like that:

 double mean = ( boxes[0] + boxes[1] + boxes[2] + boxes[3] + boxes[4] ) / 5.0;

Solution 2 : - You can use a double cast of your sum like that:

 double mean = (double)( boxes[0] + boxes[1] + boxes[2] + boxes[3] + boxes[4] ) / 5;

To improve your answer:

You can use int n=kb.nextInt(); instead of int n = Integer.parseInt(kb.nextLine());

You can count the sum in for loop like that:

int[] boxes = new int[5];
int sum=0;
for (int i = 1 ; i <= 5 ; i++)
{
System.out.print("Enter number " + i + " > ");
int n=kb.nextInt();
boxes[i-1] = n;
sum +=boxes[i-1];
}

double mean = sum / 5.0;
System.out.println("The average of those five numbers is: " + mean);

Average incorrect : decimal point always .0

4 Answers4