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Java TreeSet descendingIterator() Method with Example

TreeSet Class descendingIterator() method: Here, we are going to learn about the descendingIterator() method of TreeSet Class with its syntax and example.
Submitted by Preeti Jain, on February 20, 2020

TreeSet Class descendingIterator() method

  • descendingIterator() method is available in java.util package.
  • descendingIterator() method is used to check whether the given object (ob) exists or not in this TreeSet.
  • descendingIterator() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
  • descendingIterator() method may throw an exception at the time of checking the given object exists.
    • ClassCastException: This exception may throw when the given parameter is incompatible to compare.
    • NullPointerException: This exception may throw when the given parameter is null exists.


    public boolean contains(Object ob);


  • Object ob – represents the object (ob) to be checked for existence in this TreeSet.

Return value:

The return type of the method is boolean, it returns true when the given object (ob) exists in this TreeSet otherwise it returns false.


// Java program to demonstrate the example 
// of boolean contains(Object ob) method of TreeSet 

import java.util.*;

public class ContainsOfTreeSet {
    public static void main(String[] args) {
        // Instantiates a TreeSet object
        TreeSet < String > tree_set = new TreeSet < String > ();

        // By using add() method is to add
        // the given object of this TreeSet 

        // Display TreeSet
        System.out.println("TreeSet: " + tree_set);

        // By using descendingIterator() method is to 
        // check whether the given object exists
        // or not exists in this TreeSet
        boolean status = tree_set.contains("JAVA");

        // Display Status
        System.out.println("tree_set.contains(JAVA): " + status);


TreeSet: [C, C++, JAVA, PHP, SFDC]
tree_set.contains(JAVA): true


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