TreeSet descendingIterator() method in Java with Examples

Last Updated : 10 Oct, 2018

The descendingIterator() method of java.util.TreeSet<E> class is used to return an iterator over the elements in this set in descending order.

Syntax:

public Iterator descendingIterator()

Return Value: This method returns an iterator over the elements in this set in descending order.

Below are the examples to illustrate the descendingIterator() method

Example 1:

// Java program to demonstrate
// descendingIterator() method
// for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // create tree set object
            TreeSet<Integer> treeadd = new TreeSet<Integer>();
  
            // populate the TreeSet using add() method
            treeadd.add(10);
            treeadd.add(20);
            treeadd.add(30);
            treeadd.add(40);
  
            // Print the TreeSet
            System.out.println("TreeSet: " + treeadd);
  
            // create descending iterator
            // using descendingIterator() method
            Iterator<Integer>
                iterator = treeadd.descendingIterator();
  
            System.out.println("\nValues using DescendingIterator:");
  
            // printing the interated value
            while (iterator.hasNext()) {
                System.out.println("Value : "
                                   + iterator.next());
            }
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

TreeSet: [10, 20, 30, 40]

Values using DescendingIterator:
Value : 40
Value : 30
Value : 20
Value : 10

Example 2:

// Java program to demonstrate
// descendingIterator() method
// for String value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // create tree set object
            TreeSet<String> treeadd = new TreeSet<String>();
  
            // populate the TreeSet using add() method
            treeadd.add("A");
            treeadd.add("B");
            treeadd.add("C");
            treeadd.add("D");
  
            // Print the TreeSet
            System.out.println("TreeSet: " + treeadd);
  
            // create descending iterator
            // using descendingIterator() method
            Iterator<String>
                iterator = treeadd.descendingIterator();
  
            System.out.println("\nValues using DescendingIterator:");
  
            // printing the interated value
            while (iterator.hasNext()) {
                System.out.println("Value : "
                                   + iterator.next());
            }
        }
  
        catch (Exception e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

TreeSet: [A, B, C, D]

Values using DescendingIterator:
Value : D
Value : C
Value : B
Value : A

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