.swap()

The Collections.swap() method swaps the positions of two elements in a List.

import java.util.*;

Collections.swap(myList, index1, index2);

This will swap the element in myList at zero-based int index index1 with the element at zero-based int index index2.

The following example creates an ArrayList and then uses Collections.swap() to reorder some elements:

import java.util.*;

public class Main {
 public static void main(String[] args) {
   ArrayList<String> food = new ArrayList<String>();
   food.add("Cabbage");
   food.add("Pizza");
   food.add("Sausage");
   food.add("Potatoes");
   food.add("Salad");

   System.out.println(food);
   Collections.swap(food,2,4);
   System.out.println(food);
 }
}

This will output the following:

[Cabbage, Pizza, Sausage, Potatoes, Salad]
[Cabbage, Pizza, Salad, Potatoes, Sausage]