how sum of 2 arraylist?

Question

i got below mentioned error when run code:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
    at java.util.LinkedList.checkPositionIndex(Unknown Source)
    at java.util.LinkedList.addAll(Unknown Source)
    at Collection.Dynamycmaasiv.Collecktionaddlist.main(Collecktionaddlist.java:36)

code

public static void main(String[] args) {
    LinkedList<Integer> num = new LinkedList<Integer>();
    LinkedList<Integer> numodd = new LinkedList<Integer>();
    LinkedList<Integer> numeven = new LinkedList<Integer>();
    LinkedList<Integer> sumoffevenandodd = new LinkedList<Integer>();// help
                                                                        // me
                                                                        // to
                                                                        // solve

    for (double i = 0; i < 50; i++) {
        num.add((int) i);
        if (i % 2 == 0) {
            numeven.add((int) i);
        } else {
            numodd.add((int) i);

        }
    }

    System.out.println(num);
    System.out.println("-----------------");
    System.out.println(numodd);
    System.out.println("-----------------");
    System.out.println(numeven);

    for (int i =0; i<numeven.size(); i++){

        sumoffevenandodd.addAll(numeven.get(i)+ numodd.get(i), null);
    }

    System.out.println(sumoffevenandodd);
}

}

sumoffevenandodd.addAll(numeven.get(i)+ numodd.get(i), null); this is where the exception occurs. addAll takes a Collection as parameter, not an Integer. — QBrute
– QBrute, Commented Sep 11, 2016 at 13:00

GhostCat · Accepted Answer · 2016-09-11 13:39:34Z

2

addAll() is not about adding up numbers. It is about adding all the elements of the method parameter to the collection itself.

So, you need to loop, like

int sum = 0;
for (Integer numberFromList : numeven) {
  sum = sum + numberFromList;

Or, if you have Java8, you can use streams:

int sumEven = numeven.stream().sum();

Sum, done.

And for the record: the real lesson to be learned here: read the javadoc. Don't assume that method called addAll() does what you suppose it does. Turn to the javadoc and inform yourself what reality thinks about your assumptions.

But just to be clear; as I got carried away with your question, too.

In your code, if you change

sumoffevenandodd.addAll(numeven.get(i)+ numodd.get(i), null);

to

sumoffevenandodd.add(numeven.get(i)+ numodd.get(i));

it should work, too.

Long story short: if you intended to really have a list with 50 sums within, then my first paragraphs do not really help with your problem. But it isn't exactly clear what you wanted to do; so I leave my answer as is - to address both possible explanations what is "wrong" in your logic.

edited Sep 11, 2016 at 13:39

answered Sep 11, 2016 at 13:01

GhostCat

141k28 gold badges191 silver badges262 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

GhostCat Over a year ago

One can also say "read the question". I am not so sure any more if I am really correct with my assumptions either.

Islam Ismayilov Over a year ago

Dear GhostCat, how find difference , put minus but get no result: sumoffevenandodd.add(Collections.singletonList(numeven.get(i) - numodd.get(i)));

GhostCat Over a year ago

Sorry, that part was wrong: when you really want the sum or delta, you don't need that Collections call. Just use add(numeven.get(i) OP numodd.get(i)) where OP is +, -, *, whatever. And side note: names like evenNumbers, or oddNumbers are much better to read!

sagar routhu · Accepted Answer · 2016-09-11 13:22:44Z

1

if the intention of the question is

num odd

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49]

num even

[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48]

sum of odd and even

[1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93, 97]

then

for (int i =0; i< numeven.size(); i++){

        sumoffevenandodd.add(numeven.get(i)+ numodd.get(i));
    }

answered Sep 11, 2016 at 13:22

sagar routhu

674 bronze badges

Collectives™ on Stack Overflow

how sum of 2 arraylist?

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related