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

// 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); 
        } 
    } 
} 

Output:

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

Example 2: For Reverse ordering

// 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); 
        } 
    } 
} 

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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