TreeMap comparator() method in Java with Examples

The comparator() method of java.util.TreeMap class is used to return the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.

Syntax:

public Comparator comparator()

Return Value: This method returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys



Below are the examples to illustrate the descendingIterator() method

Example 1: For Natural ordering

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// Java program to demonstrate
// comparator() method for natural ordering
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
  
        try {
  
            // creating object of TreeMap
            NavigableMap<Integer, String>
                treemap = new TreeMap<Integer, String>();
  
            // populating tree map
            treemap.put(1, "one");
            treemap.put(2, "two");
            treemap.put(3, "three");
            treemap.put(4, "four");
            treemap.put(5, "five");
  
            // pritnig the TreeMap
            System.out.println("TreeMap: " + treemap);
  
            // getting used Comparator in the map
            // using comparator() method
            Comparator comp = treemap.comparator();
  
            // pritnig the comparator value
            System.out.println("Comparator value: "
                               + comp);
        }
  
        catch (NullPointerException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:


TreeMap: {1=one, 2=two, 3=three, 4=four, 5=five}
Comparator value: null





Example 2: For Reverse ordering











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// Java program to demonstrate 


// comparator() method 


// for reverse ordering 


  


import java.util.*; 


  


public class GFG1 { 


    public static void main(String[] argv) 


        throws Exception 


    { 


  


        try { 


  


            // creating object of TreeMap 


            NavigableMap<Integer, String> 


                treemap = new TreeMap<Integer, String>( 


                    Collections.reverseOrder()); 


  


            // populating tree map 


            treemap.put(1, "one"); 


            treemap.put(2, "two"); 


            treemap.put(3, "three"); 


            treemap.put(4, "four"); 


            treemap.put(5, "five"); 


  


            // pritnig the TreeMap 


            System.out.println("TreeMap: " + treemap); 


  


            // getting used Comparator in the map 


            // using comparator() method 


            Comparator comp = treemap.comparator(); 


  


            // pritnig the comparator value 


            System.out.println("Comparator value: " + comp); 


        } 


  


        catch (NullPointerException e) { 


            System.out.println("Exception thrown : " + e); 


        } 


    } 


} 



















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Output:


TreeMap: {5=five, 4=four, 3=three, 2=two, 1=one}
Comparator value: java.util.Collections$ReverseComparator@232204a1





Output:


Comparator value: java.util.Collections$ReverseComparator@232204a1



          
          
          
          

            

    

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