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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