SortedMap comparator() method in Java with Examples (original) (raw)

Last Updated : 08 Jun, 2021

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.

Java `

// 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");

        // Printing the SortedTreeMap
        System.out.println("SortedTreeMap: " + sotreemap);

        // Getting used Comparator in the map
        // using comparator() method
        Comparator comp = sotreemap.comparator();

        // Printing the comparator value
        System.out.println("Comparator value: "
                           + comp);
    }

    catch (NullPointerException e) {
        System.out.println("Exception thrown : " + e);
    }
}

}

`

Output:

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

Example 2: For Reverse ordering.

Java `

// Java program to demonstrate // comparator() method // for reverse ordering

import java.util.*;

public class GFG1 { public static void main(String[] argv) throws Exception

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]

{

    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");

        // Printing the TreeMap
        System.out.println("SortedTreeMap: " + sotreemap);

        // Getting used Comparator in the map
        // using comparator() method
        Comparator comp = sotreemap.comparator();

        // Printing the comparator value
        System.out.println("Comparator value: " + comp);
    }

    catch (NullPointerException e) {
        System.out.println("Exception thrown : " + e);
    }
}

}

`

Output:

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