Program to Sort Set by using TreeSet(we will define Comparator to sort elements in descending order), where elements are Integer type.

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TreeSet is sorted by natural order of elements (i.e. in ascending order), but we will implement Comparator interface and change the behaviour to sort elements in descending order.

import java.util.Comparator; import java.util.Set; import java.util.TreeSet; /** * @author AnkitMittal * Copyright (c), AnkitMittal JavaMadeSoEasy.com * Main class */ public class SortSet {    public static void main(String...a){        Set<Integer> treeSet = new TreeSet<Integer>(new Comparator<Integer>() {                  @Override                  public int compare(Integer o1, Integer o2) {                        //using Comparator to sort elements in descending order.                        return o2.compareTo(o1);                  }           });        treeSet.add(3);        treeSet.add(1);        treeSet.add(2);        System.out.println("treeSet : "+treeSet);           } } /*OUTPUT treeSet : [3, 2, 1] */

Labels: Collection programs Comparable and Comparator program Core Java