Use a Variable Argument to find the Product of Numbers without ArrayList?

Question

I am practicing with variable arguments and I want to be able to find the product of numbers. This is the first way that I could figure out how to do it. I feel like I can do it without using an ArrayList, but I just can't see how.

import java.util.*;

public class variableMethod
{
    public static void main(String[] satharel)
    {
        System.out.printf("The product of 5 and 10: \t\t%3d%n", productFinder(5, 10));
        System.out.printf("The product of 2 and 3 and 4: \t\t%3d%n", productFinder(2, 3, 4));
        System.out.printf("The product of 1 and 2 and 3: \t\t%3d%n", productFinder(1, 2, 3));
        System.out.printf("The product of 7 and 2 and 4 and 5: \t%3d%n", productFinder(7, 2, 4, 5));

    }

    public static int productFinder(int... num)
    {
        ArrayList<Integer> numbers = new ArrayList<Integer>();

        for(int n : num)
            numbers.add(n);

        int first = numbers.get(0);

        for(int i = 1; i < numbers.size(); i++)
            first *= numbers.get(i);

        return first;
    }
}

Suresh Atta · Accepted Answer · 2017-02-17 06:54:57Z

3

Surely you dont need a list there. Just iterate over array and make product.

public static int productFinder(int... num) {
        int result = 1;
        for (int i = 0; i < num.length; i++) {
            result *= num[i];
        }
        return result;
    }

edited Feb 17, 2017 at 6:54

answered Feb 17, 2017 at 6:49

Suresh Atta

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3 Comments

Dirk Over a year ago

I'd probably start with result == 1

Suresh Atta Over a year ago

@Dirk Thankyou life saver :D

atlantoc Over a year ago

Wow. Why could I not see such a simple answer? Thank you so much! I love the simplicity of this.

Community · Accepted Answer · 2017-05-23 12:16:59Z

1

Yes you can, variable arguments are treated as arrays see this answer so you can iterate them like a normal array:

public static int productFinder(int... num)
{
    int product = 1;
    for(int i = 0; i < num.length; i++) {
        product *= num[i];
    }
    return product;
}

edited May 23, 2017 at 12:16

CommunityBot

11 silver badge

answered Feb 17, 2017 at 6:57

Fahad

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1 Comment

atlantoc Over a year ago

Ah, that's very helpful! Except I would write "product *= num[i]" instead of "product *= num[1]"

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