[알고리즘] ArrayList<Integer> -> int[]

ArrayList to Array

1. stream(java8)

String[] stArr = stLst.stream().toArray(String[]::new);

2. List method

String[] stArr = stLst.toArray(new String[stLst.size()]);

Array to ArrayList

List<String> stLst = Arrays.asList(stArr);

Integer ArratList -> int[]

mapToInt 이용

int[] array = list.stream().mapToInt(i->i).toArray();
int[] array = list.stream().mapToInt(Integer::intValue).toArray();