Is there a way in Java to pop an Integer object out of an arrayList and then place it in another arr-CodePudding

For example, myArrayList is [1, 1, 1], is there a function which removes a 1 from myArray and then places it in myArrayList2 so that:

myArrayList [1, 1]
myArrayList2 [1]

CodePudding user response：

There are multiple ways to do this. For any mutable List, you could use the listIterator():

To remove from the front:

private static void moveGeneralList() {
    List<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2, 3));
    List<Integer> list2 = new ArrayList<>();

    ListIterator<Integer> iterator = list1.listIterator();
    if (iterator.hasNext()) {
        list2.add(iterator.next());
        iterator.remove();
    }

    System.out.println(list1);
    System.out.println(list2);
}

Output:

[2, 3]
[1]

To remove from the end:

private static void moveGeneralListReversed() {
    List<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2, 3));
    List<Integer> list2 = new ArrayList<>();

    ListIterator<Integer> iterator = list1.listIterator(list1.size());
    if (iterator.hasPrevious()) {
        list2.add(iterator.previous());
        iterator.remove();
    }

    System.out.println(list1);
    System.out.println(list2);
}

Output:

[1, 2]
[3]

You can also use LinkedList/Deque specific methods like pop to remove from the start of the list:

private static void linkedListPop() {
    LinkedList<Integer> list1 = new LinkedList<>(Arrays.asList(1, 2, 3));
    List<Integer> list2 = new ArrayList<>();

    list2.add(list1.pop());

    System.out.println(list1);
    System.out.println(list2);
}

Output:

[2, 3]
[1]

And other combinations are possible, of course (e.g. using removeLast(), addFirst() (when using a Deque), etc.).

Doing this with an immutable list will result in an exception (UnsupportedOperationException).