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Swap List elements example

This is an example of how to swap a List’s elements . We are using the swap(List list, int i, int j) method of the Collections Class. Collections provides static methods that operate on or return collections. We are also using the ArrayList as a List implementation, but the same API applies to any type of List implementation classes e.g. Vector etc. Swaping the elements of a List implies that you should:

  • Create a new ArrayList.
  • Populate the list with elements, with the add(E e) API method of the ArrayList.
  • Invoke the swap(List list, int i, int j) API method of the Collections to swap the elements of the list. In the example we swap the element in position 1 of the list with the one in position 3. It swaps the elements at the specified positions in the specified list.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;
 
import java.util.ArrayList;
import java.util.Collections;
 
public class SwapList {
 
  public static void main(String[] args) {

    /*

Please note that the same API applies to any type of 

List implementation classes e.g. Vector etc

*/

    // Create an ArrayList and populate it with elements
    ArrayList arrayList = new ArrayList();
    arrayList.add("element_1");
    arrayList.add("element_2");
    arrayList.add("element_3"); 
    arrayList.add("element_4"); 
    arrayList.add("element_5"); 

    System.out.println("ArrayList elements : " + arrayList);

    /*

static void swap(List list, int firstElementIndex, int secondElementIndex)

operation swaps the two elements of the provided List that are at 

firstElementIndex and secondElementIndex positions respectively
    */
    Collections.swap(arrayList,1,3);
 
    System.out.println("ArrayList elements after swapping : " + arrayList);
 
  }
}

Output:

ArrayList elements : [element_1, element_2, element_3, element_4, element_5]
ArrayList elements after swapping : [element_1, element_4, element_3, element_2, element_5]

 
This was an example of how to swap the elements of a List in Java.

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