Collections
Reverse order of List example
With this example we are going to demonstrate how to reverse the order of a List. This is provided by the reverse(List> list)
API method of the Collections class. The ArrayList is used as a List implementation, but the same API applies to any type of List implementation classes e.g. Vector etc. In short, to reverse the order of a List you should:
- Create a new ArrayList.
- Populate the list with elements, with the
add(E e)
API method of the ArrayList. - Reverse the elements of the list, invoking the
reverse(List list)
API method of the Collections.
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 ReverseListOrder { 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 reverse(List list) method reverses the order of elements of the specified list. Collections.reverse(arrayList); System.out.println("ArrayList elements after reversing order : " + arrayList); } }
Output:
ArrayList elements : [element_1, element_2, element_3, element_4, element_5]
ArrayList elements after reversing order : [element_5, element_4, element_3, element_2, element_1]
This was an example of how to reverse the order of a List in Java.