how to convert an array list to a list of ints in java code example

Example 1: convert list of integer to array in java

List<Integer> al = new ArrayList<Integer>(); 
Integer[] arr = new Integer[al.size()]; 
arr = al.toArray(arr);

Example 2: convert int array to integer list java

int[] arr = {1,2,3};
IntStream.of(arr).boxed().collect(Collectors.toList());