CODEWITHSUNDEEP
java
Casper Lindberg
Casper Lindberg

Reputation: 1103

Java: Dividing integers to double doesn't work

public class SumAndAverage {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int sum = 0;
        int num;
        for(num = 0; num <= 100; num++){ 
            sum += num; 
        }

        double average = ((double)sum) / num;
        System.out.println("The sum is " + sum);
        System.out.println("The average is " + average);

    }
}

RESULT:

The sum is 5050 The average is 50.0

What's wrong:

5050 / 100 = 50.5 NOT 50.0

Upvotes: 1

Views: 177

Answers (3)

Vivek
Vivek

Reputation: 3613

Variable num will be 101 when it comes out of loop. So you need to manually subtract one or below can do the same job better with one iteration less

for(num = 0; num < 100; ){ 
    sum += ++num; 
}

Full Program

public class SumAndAverage {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int sum = 0;
    int num;
    for(num = 0; num < 100; ){ 
        sum += ++num; 
    }

    double average = ((double)sum) / num;
    System.out.println("The sum is " + sum);
    System.out.println("The average is " + average);
}
}

Check it.

Upvotes: 0

Dariusz
Dariusz

Reputation: 22241

You got it wrong. That's what happens when you don't use variables as loop checks (and when you use magic numbers anti-pattern in general)- and reuse those later. That way you are certain what value you will actually use.

public class SumAndAverage {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int sum = 0;
        int num;
        int max = 100;
        for(num = 0; num <= max; num++){ 
            sum += num; 
        }

        double average = ((double)sum) / max;
        System.out.println("The sum is " + sum);
        System.out.println("The average is " + average);

    }
}

Your num was equal to 101, not 100...

Upvotes: 0

Denys S&#233;guret
Denys S&#233;guret

Reputation: 382150

When this loop finishes

for(num = 0; num <= 100; num++){

num is 101, not 100. Because what happens is that the condition is tested until it's false, and this happens when num>100.

Upvotes: 6

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