ArrayList.md

ArrayList

Initialization

List<Integer> arrayList = new ArrayList<>();

List<Integer> arrayList = new ArrayList<>(Arrays.asList(1, 2, 3));

List<List<Integer>> listOfList = new ArrayList<>();

Print

for (int elem : arrayList) {
    System.out.println(elem);
}

for (List<Integer> list : listOfList) {
    for (int elem : list) {
        System.out.println(elem);
    }
}

Sort in ascending order

Collections.sort(arrayList);

Sort in ascending order

Collections.sort(arrayList, Collections.reverseOrder());

Get a value at index i

List<Integer> foo = new ArrayList<>();
int bar = foo.get(0);

Create a deep copy of a list

List<String> oldList = new ArrayList<>();
List<String> newList = new ArrayList<>(oldList);

List of List

List<List<String>> myList = new ArrayList<>();