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 orderingimport 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 orderingimport java.util.*;public class GFG1 { public static void main(String[] argv) throws Exception<div class="code-output"><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"); // 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