Arrays class

List list = Arrays.asList(new Integer[]{1,2,3,4,5});

List list = Arrays.asList(1,2,3,4,5);

==> 읽기 전용이라서 변경 불가 이므로 

list.add(8) // UnsupportedOperationException 예외 발생

 

List list = new ArrayList(Arrays.asList(1,2,3,45,6));   // 이렇게 해야함

 

이차원 배열 출력은

Arrays.deepToString(arr2D);   

배열 비교

Arrays.equals(arr1, arr2);

Arrays.deepEquals(arr2D1, arr2D2);

 

int[] arrCopy = Arrays.copyOfRange(arr, 2, 4);

 

int[] arr = new int[5];

Arrays.fill(arr, 9); // [9,9,9,9,9]

Arrays.setAll(arr, i -< (int)(Math.random()*19) +1);

 

binary search는 반드시 정렬 후에 해야함

 

import java.util.ArrayList;
import java.util.Collections;

public class ArrayListEx {
  public static void main(String[] args) {
    ArrayList<Integer> arrayList = new ArrayList<>();
    arrayList.add(3);    arrayList.add(5);    arrayList.add(9);
    arrayList.add(19);    arrayList.add(1);    arrayList.add(2);
    arrayList.add(23);

    arrayList.add(Integer.parseInt("3"));
    arrayList.add(49);
    System.out.println(arrayList.indexOf(19));
    arrayList.set(2, 15);
    arrayList.add(3, 29);
    arrayList.remove(4);

    ArrayList<Integer> arrSub = new ArrayList<>(arrayList.subList(1, 4));

    System.out.println(arrayList.containsAll(arrSub));

    Collections.sort(arrayList);
    System.out.println(arrayList);
    System.out.println(arrSub);

    for (int i = arrayList.size() -1; i >=0; i--) {
      if (arrSub.contains(arrayList.get(i))) {
        arrayList.remove(i);
      }
    }

    Object copyList =  arrayList.clone();
    System.out.println(copyList);
    ArrayList<? extends Integer> copiedList = (ArrayList<Integer>) copyList;
    System.out.println(copiedList);
    
    System.out.println(arrayList);
  }
}