How to solve this ArrayList issue?

Question

I have searched around the internet and what I am doing seems to be the standard conversion operation, but it still tells me:

Cannot resolve constructor 'ArrayList(java.util.List<T>)'

I also have no issues with String array conversions when done in same way. This is my code:

public class Main {

    public static void main(String[] args) {
        int[] arr = {1, 10, 1, 30, 50, 30};
        ArrayList<Integer>  arrList = new ArrayList<Integer>(Arrays.asList(arr));
        System.out.println(arrList);
    }
}

Any ideas?

Are you including both import `java.util.ArrayList` and `import java.util.Arrays`? — Eric, Feb 28 '20 at 07:38
Note that since there's not auto boxing for primitive arrays `Arrays.asList(arr)` will create a `List` instead of a `List`. — Thomas, Feb 28 '20 at 07:40
Does this answer your question? [Converting array to list in Java](https://stackoverflow.com/questions/2607289/converting-array-to-list-in-java) — Alexandru Somai, Feb 28 '20 at 07:43
On my machine I'm using Java's 8 (target compatibility 1.8) and it compiles without a problem, so maybe the solution for your case is to upgrade your target to the newer Java's version — Eric, Feb 28 '20 at 07:54

score 1 · Accepted Answer · answered Feb 28 '20 at 07:42

1

This should work:

public static void main(String []args){
    Integer[] arr = {1, 10, 1, 30, 50, 30};
    ArrayList<Integer>  arrList = new ArrayList<Integer>(Arrays.asList(arr));
    System.out.println(arrList);
}

answered Feb 28 '20 at 07:42

Buddy Christ

1,364
8
22

Thanks, this is definitely the simplest method. – Irakli Feb 28 '20 at 07:51

score 0 · Answer 2 · answered Feb 28 '20 at 07:43

Note that since there's not auto boxing for primitive arrays Arrays.asList(arr) will create a List<int[]> instead of a List<Integer>.

If you want to convert that array to a List<Integer> try this:

//instead of boxed() you could use one of the mapToXX methods 
List<Integer>  arrList = Arrays.stream(arr).boxed().collect(Collectors.toList());

score 0 · Answer 3 · answered Feb 28 '20 at 07:49

ArrayList<Integer> constructor takes Integer as an object not a primitive array. you don't have issues with Strings since Strings are already reference type (Objects). All you need to do is to create the array arr as Integer.

Integer[] arr = new Integer[] {1, 10, 1, 30, 50, 30};

score 0 · Answer 4 · answered Feb 28 '20 at 07:50

0

Hope below code will help you.

        int[] arr = {1, 10, 1, 30, 50, 30};
        ArrayList<Integer> arrList = IntStream.of(arr)
                .boxed().collect(Collectors.toCollection(ArrayList::new));
        System.out.println(arrList);

answered Feb 28 '20 at 07:50

chaitanya dalvi

1,539
2
17
25

How to solve this ArrayList issue?

4 Answers4