[Java] Set to Array & ArrayList to Array

HashSet -> ArrayList -> Array

HashSet<Integer> set = new HashSet<>(); //Set

ArrayList<Integer> list = new ArrayList<>(set); //Set -> ArrayList

Collections.sort(list); //정렬
        
int[] answer = new int[list.size()];

for(int i = 0; i < list.size(); i++) { //ArrayList -> Array
	answer[i] = list.get(i);
}

 

위의 코드를 아래처럼 한줄로 가능

 

return set.stream().sorted().mapToInt(Integer::intValue).toArray();

ArrayList -> Array

ArrayList<Integer> list = new ArrayList<>();
int[] arr = new int[list.size()];
list.toArray(arr);