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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