SortedMap comparator() method in Java with Examples

The comparator() method of java.util.SortedMap interface 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 programs illustrate the comparator() 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 SortedTreeMap
            SortedMap<Integer, String>
                sotreemap = new TreeMap<Integer, String>();
  
            // Populating tree map
            sotreemap.put(1, "one");
            sotreemap.put(2, "two");
            sotreemap.put(3, "three");
            sotreemap.put(4, "four");
            sotreemap.put(5, "five");
  
            // Pritnig the SortedTreeMap
            System.out.println("SortedTreeMap: " + sotreemap);
  
            // Getting used Comparator in the map
            // using comparator() method
            Comparator comp = sotreemap.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:

SortedTreeMap: {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<div class = 'outputDiv'>
<b>Output:</b>
<pre>
Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The set is: [10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You]
</pre>
</div>
  
    {
  
        try {
  
            // Creating object of TreeMap
            SortedMap<Integer, String>
                sotreemap = new TreeMap<Integer, String>(
                    Collections.reverseOrder());
  
            // Populating tree map
            sotreemap.put(1, "one");
            sotreemap.put(2, "two");
            sotreemap.put(3, "three");
            sotreemap.put(4, "four");
            sotreemap.put(5, "five");
  
            // Pritnig the TreeMap
            System.out.println("SortedTreeMap: " + sotreemap);
  
            // Getting used Comparator in the map
            // using comparator() method
            Comparator comp = sotreemap.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:

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


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