[Java] List<Integer> To int[]

1. For문

public static void main(String[] args) {
    List<Integer> list = Arrays.asList(1,2,3,4,4,5,5,6);

    int[] arr = new int[list.size()];
    for( int i=0; i<list.size(); i++ ) {
        arr[i] = list.get(i);
    }

    System.out.println(Arrays.toString(arr));
}

public static void main(String[] args) {
    List<Integer> list = Arrays.asList(1,2,3,4,4,5,5,6);

    int[] arr = new int[list.size()];
    Iterator<Integer> iterator = list.iterator();

    for( int i=0; i<list.size(); i++ ) {
        arr[i] = iterator.next().intValue();
    }

    System.out.println(Arrays.toString(arr));
}

 

2. stream()

public static void main(String[] args) {
    List<Integer> list = Arrays.asList(1,2,3,4,4,5,5,6);

    int[] arr = list.stream().mapToInt(Integer::intValue).toArray();

    System.out.println(Arrays.toString(arr));
}

public static void main(String[] args) {
    List<Integer> list = Arrays.asList(1,2,3,4,4,5,5,6);

    int[] arr = list.stream().mapToInt(i -> i).toArray();

    System.out.println(Arrays.toString(arr));
}

 

 

🙏 참조 ::

• http://daplus.net/java-%EC%A0%95%EC%88%98%EB%A5%BC-%ED%8F%AC%ED%95%A8%ED%95%98%EB%8A%94-arraylist%EB%A5%BC-%EA%B8%B0%EB%B3%B8-int-%EB%B0%B0%EC%97%B4%EB%A1%9C-%EB%B3%80%ED%99%98%ED%95%98%EB%8A%94-%EB%B0%A9%EB%B2%95/