Get array sum and return the value through a method in JAVA

Question

I have this code sample with a method which returns the sum of array values. But instead of the sum, I'm getting 0.

This is my code sample

class Calculation {

    int answer;

    public int SumOfArrays(int data[], int size) {
        answer = 0;
        for (int i = data[0]; i < size; i++) {
            answer += data[i];
            //System.out.println(data[i]);
        }        
        return answer;
    }

class Main {

    public static void main(String[] args) {
        Calculation cal = new Calculation();
        int data[]={10,20};
        System.out.println(cal.SumOfArrays(data, 2));            
    }
}

can anyone tell me what;s wrong with my code?

Why should i be initialized to data[0]? i is supposed to be the index in the array. Not a value of the array. And why do you pass size as argument? The size of the array is data.length. No need for an additional parameter. docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html, docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html — JB Nizet
– JB Nizet, Commented Feb 24, 2018 at 16:09
size is the array size. without using data.length I need to set array size manually as a parameter in the method. — Jananath Banuka
– Jananath Banuka, Commented Feb 24, 2018 at 16:12
System.out.println(Arrays.stream(data).sum()); Don't reinvent the wheel. And if you must reinvent the wheel, use a for-each loop. — Elliott Frisch
– Elliott Frisch, Commented Feb 24, 2018 at 16:13
No, you don't. If I give you my car, I don't need to give you a paper with the color of my car. You can know its color by just looking at the car. If you receive an array, you can know its length by looking at the value of its length attribute. Passing an additional parameter is redundant. — JB Nizet
– JB Nizet, Commented Feb 24, 2018 at 16:14

Andrew · Accepted Answer · 2018-02-24 16:11:21Z

1

The loop doesn't run at all - the condition data[0] < size is false, so the initial value of answer = 0 is returned.

To make it work, change the statement to (int i = 0; i < size; i++). Also, size might be replaced with data.length.

answered Feb 24, 2018 at 16:11

Andrew

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1 Comment

Andrew Over a year ago

@user8794865, if you set size manually, you need to validate it to make sure it is within the bounds [0, data.length)

ikos23 · Accepted Answer · 2018-02-24 16:13:27Z

1

This is your code with minor corrections. Try it.

class Calculation {

    public int SumOfArrays(int data[]) {
        int answer = 0; // this is just better
        for (int i = 0; i < data.length; i++) {
            answer += data[i];
        }        
        return answer;
    }

class Main {

    public static void main(String[] args) {
        Calculation cal = new Calculation();
        int data[]={10,20};
        System.out.println(cal.SumOfArrays(data));            
    }
}

answered Feb 24, 2018 at 16:13

ikos23

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3 Comments

Jananath Banuka Over a year ago

I need to input array size manually. How can I do that without omitting the size parameter?

ikos23 Over a year ago

@user8794865 why do you need this? if you want to calculate only sum of the first few elements then you need it, otherwise array has length that returns its size

ikos23 Over a year ago

if you still need the second parameter, just add it as it was SumOfArrays(int data[], int size) and also add it here for (int i = 0; i < size; i++) and in Main cal.SumOfArrays(data, 2) - as it was before

Sanjeev Sachdev · Accepted Answer · 2018-02-24 16:14:17Z

1

The counter i for the for loop is incorrectly initialized. You have initialized it to the value of first element in the array instead of 0. Initialize it to 0 as shown below:

    for (int i = 0; i < size; i++) {
        answer += data[i];
        //System.out.println(data[i]);
    }

answered Feb 24, 2018 at 16:14

Sanjeev Sachdev

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Comments

FRe34 · Accepted Answer · 2018-02-24 16:27:57Z

0

As you can see from your loop for(int i = data[0]; i < size; i++) the variable i is equals to the first element in the data array which means that is greater then the size variable ..so the loop will not begin at all to fix the problem change your loop to this

   for (int i = 0; i < size; i++) {
        answer += data[i];
        //System.out.println(data[i]);
    }

answered Feb 24, 2018 at 16:27

FRe34

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