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Java Collections reverse() Method with Example

Collections Class reverse() method: Here, we are going to learn about the reverse() method of Collections Class with its syntax and example.
Submitted by Preeti Jain, on February 04, 2020

Collections Class reverse() method

• reverse() method is available in java.util package.
• reverse() method is used to reverse the order of its elements of the given list(l) or in other words, we can say this method is used to change the order of its elements starting from the right side.
• reverse() method is a static method, so it is accessible with the class name and if we try to access the method with the class object then we will not get an error.
• reverse() method may throw an exception at the time of reversing the order its elements of the list.
  UnsupportedOperationException: This exception may throw when the given list un-support set operation.

Syntax:

    public static void reverse(List l);

Parameter(s):

• List l – represents the list whose elements order are to be reversed.

Return value:

The return type of this method is void, it returns nothing.

Example:

// Java program is to demonstrate the example of
// reverse(List l) method of Collections

import java.util.*;

public class ReverseOfCollections {
    public static void main(String args[]) {
        // Instatiates a array list object
        List < Integer > arr_l = new ArrayList < Integer > ();

        // By using add() method is to add
        // objects in an array list 
        arr_l.add(10);
        arr_l.add(20);
        arr_l.add(30);
        arr_l.add(40);
        arr_l.add(50);

        // Display ArrayList
        System.out.println("Array List : " + arr_l);

        // By using reverse() method is to
        // reverse the order of elements
        Collections.reverse(arr_l);

        // Display Reversible ArrayList
        System.out.println("Collections.reverse(arr_l): " + arr_l);
    }
}

Output

Array List : [10, 20, 30, 40, 50]
Collections.reverse(arr_l): [50, 40, 30, 20, 10]