Summing ArrayList values

Question

Ok, so far my program allows user input, recognizes how many numbers are stored in the array list and then outputs those numbers that are stored. How can I sum all the numbers entered by the user?

import java.util.Scanner;
import java.util.ArrayList;

public class lab5 
{
    public static void main (String[]args)
    {
        Scanner userInput = new Scanner(System.in);

        ArrayList<Integer> list = new ArrayList<>();

        //Creates initial value for nextInt variable
        int nextInt = -1; 

        //Create loop to store user input into array list until 0 is entered
        while((nextInt = userInput.nextInt()) != 0)
        {
            list.add(nextInt);
        }

        //Calculate average once zero is inputted
        if (nextInt == 0)
        {
            System.out.println("There are " + list.size() + " numbers in this array list");
            System.out.println("The numbers are " + list);
            System.out.println("The sum of the number are ")
        }
    }
}

[Possibly duplicate](http://stackoverflow.com/questions/16242733/sum-all-the-elements-java-arraylist), except that using an `ArrayList` at all in unnecessary. — Bernhard Barker, Sep 24 '13 at 16:58

score 0 · Accepted Answer · answered Sep 24 '13 at 16:32

0

You're close! All the numbers that are inputted to your program will reside in nextInt at some point. How can you use that fact to get the sum? Hint: you'll need to keep track of the sum outside of the while loop.

answered Sep 24 '13 at 16:32

musical_coder

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Do I store the values outside to a new array? I'm so new at this :( – Ryan Sep 24 '13 at 16:39
Not quite (you're already doing that with `list`). Picture this: your job is to wait by the door while people bring their dogs into a pet shop, and count how many dogs come in over the span of an hour. Each person could bring one or more dogs (you don't know in advance, you just count the dogs when they come in). So if you were in that situation, you would keep a SINGLE running tally in your head. How can you represent that single tally as a Java variable? – musical_coder Sep 24 '13 at 16:48
So would I want to change it to a for loop and add a counter in the parameters. I'm so confused. – Ryan Sep 24 '13 at 17:06
Hang in there man; like I said, you're actually really close. The loop you have is fine as-is. It MUST be a `while` loop, because you want to be able to keep going indefinitely (until someone enters 0). A `for` loop isn't really appropriate for that. Not sure what you mean by the parameters, but right above the `while` loop, add `int totalSum = 0;`. Inside the loop, add to that sum every time you see a new value. Hint: that will look something like `totalSum = totalSum + X;`. I leave it to you to replace X with the correct variable. – musical_coder Sep 24 '13 at 17:18
1

I GOT IT! I was thinking way too hard about this. totalSum = totalSum + nextInt; – Ryan Sep 24 '13 at 17:24
Great! Another way would be to calculate those values from the ArrayList after you've exited the main while loop. Note that the check `if (nextInt == 0)` is unnecessary since that's the only way the while loop will exit. – Meesh Sep 24 '13 at 17:29
@Ryan Schachte: knew you could do it! If you found my answers and comments useful, please check off my answer as accepted. – musical_coder Sep 24 '13 at 17:32
When you say calculate, I don't know how I calculate each array list, since the number is not pre-defined. How can I go about doing that for this instance? Also, I see now my if test is unnecessary, thanks! – Ryan Sep 24 '13 at 17:32

Summing ArrayList values

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