How move first item of arraylist to last position?

Question

my code move to last arraylist:

 if (listItem.get(listItem.size() - 1).SortNo > 0) {
                    while (listItem.get(0).SortNo == 0) {

                        DTO_NightClinic dt = listItem.get(0);
                        listItem.remove(0);
                        listItem.add(dt);
                    }
                }

But common listItem.remove(0); it not working. and first item still exist at first position of arraylist.

Answer 1

Collections.rotate(list, -1);

Just use rotate with -1 place and it will do what you want

Input:

1, 2, 3, 4

Output:

2, 3, 4, 1

For more on Collections#rotate(java.util.List,int)

Answer 2

Perhaps Collections.rotate() seems to feasible solution but it is some want extended task... see the source of Collections.roatate()

public static void rotate(List<?> lst, int dist) {
      ...............
        reverse(sublist1);
        reverse(sublist2);
        reverse(list);
}

it iterates through all Items of List and applies Collections.reverse() opearion thus consumes some time.

and here, as you are simply want to remove the first item from List and add it to the tail of List, You can do a simple trick like below sample...

    ArrayList<Integer> arrayList = new ArrayList<Integer>();
    for (int i = 1; i < 5; i++) {
        arrayList.add(Integer.valueOf(i));
    }
    System.out.println(arrayList.toString());
    // prints [1, 2, 3, 4]

    Integer removedItem = arrayList.remove(0);
    arrayList.add(removedItem); // adds to the end of the List
    System.out.println(arrayList.toString());
    // prints [2, 3, 4, 1]