how to access the integer array using arraylist

Question

The error is, that it is showing a red line in Collections.addAll(in,n). How do I solve this?

ArrayList<Integer> in = new ArrayList<>(); //declared array in integer type
int[] n = getResources().getIntArray(R.array.number12);
Collections.addAll(in,n); //this is not working showing error,it is not accepting

integers.xml

<resources>
    <integer-array name="number12">
        <item>735895698</item>`
        <item>814895046</item>``
    </integer-array>
</resources>

Answer 1

This doesn't work, because an int[]-array is not an Integer[]-array, which Collections.addAll() expectes.

here are two ways to create a list from an array. This uses a for-each loop which iterates over the array and then adds every int in the array to the list:

int[] n = getResources().getIntArray(R.array.number12);
List<Integer> list = new ArrayList<>(n.length);

for(int i : n){
    list.add(i);
}

The other way, is to use the in Java8 introduced Arrays.stream():

int[] n = getResources().getIntArray(R.array.number12);
List<Integer> list = Arrays.stream(n)
    .boxed()
    .collect(Collectors.toList());

And if you explicitly want to get an ArrayList you can use the following:

int[] n = getResources().getIntArray(R.array.number12);
List<Integer> list = Arrays.stream(n)
    .boxed()
    .collect(Collectors.toCollection(ArrayList::new));

Answer 2

Quick fix:

ArrayList<Integer> in= new ArrayList<>();//declared array in integer type
Integer[] n=getResources().getIntArray(R.array.number12);
Collections.addAll(in,n);//this is not working showing error,it is not 

As explained here, the type needs to be the same. The Collection expects an array of Integer, not an array of int