Java : Collection Framework : Collections (ReverseOrder Comparator null)

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CollectionsExample.java

import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;

/*
 Method 

 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp)

 Parameters:

 cmp - a comparator who's ordering is to be reversed by the returned comparator or null

 Returns:

 A comparator that imposes the reverse ordering of the specified comparator.

 */

public class CollectionsExample
{

    public static void main(String[] args)
    {

        LinkedList<Integer> linkedList = new LinkedList<Integer>();

        linkedList.add(2);
        linkedList.add(1);
        linkedList.add(4);
        linkedList.add(3);

        System.out.println("linkedList before Sort " + linkedList+"\n");

        /*
         * Returns a comparator that imposes the reverse ordering of the
         * specified comparator. If the specified comparator is null, this
         * method is equivalent to reverseOrder() (in other words, it returns a
         * comparator that imposes the reverse of the natural ordering on a
         * collection of objects that implement the Comparable interface).
         */
        Comparator<Integer> reverseOrderComparator = Collections.reverseOrder(null);

        // sort the list
        Collections.sort(linkedList, reverseOrderComparator);

        System.out.println("linkedList sorted in ReverseOrder: " + linkedList);

    }
}

Output

linkedList before Sort [2, 1, 4, 3]

linkedList sorted in ReverseOrder: [4, 3, 2, 1]

To Download CollectionsDemo-ReverseOrderNullComparator Project Click the below link
https://sites.google.com/site/javaee4321/java-collections/CollectionsDemo-ReverseOrderNullComparator.zip?attredirects=0&d=1

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