The descendingKeySet() method of TreeMap class returns a reverse order NavigableSet view of the keys contained within the map. The iterator of the set returns the keys in descending order.
Note: The set is backed by the map, so changes to the map are reflected within the set, and vice-versa.
Syntax:
public NavigableSet<K> descendingKeySet()
Parameters: The method does not take any parameters.
Return Value: The method returns a navigable set view of the values contained in the map.
Exception: The method does not throw any exceptions.
Example 1:
// Java Program to show the working
// of descendingKeySet() Method
import java.io.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// creating tree map of Integer and String
TreeMap<Integer, String> treemap
= new TreeMap<Integer, String>();
// populating tree map using put()
treemap.put(3, "three");
treemap.put(1, "one");
treemap.put(2, "two");
treemap.put(0, "zero");
treemap.put(7, "seven");
treemap.put(6, "six");
// putting values in navigable set
// use of descendingKeySet
NavigableSet set1 = treemap.descendingKeySet();
System.out.println("Navigable set values are: "
+ set1);
}
}
Output:
Navigable set values are: [7, 6, 3, 2, 1, 0]
Example 2:
// Java Program to show the working
// of descendingKeySet() Method
import java.io.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// creating tree map of Integer and String
TreeMap<Integer, String> geeks
= new TreeMap<Integer, String>();
// putting values in navigable set
geeks.put(1, "Guru");
geeks.put(2, "Ayush");
geeks.put(3, "Devesh");
geeks.put(4, "Kashish");
System.out.println("TreeMap values :- " + geeks);
// use of descendingKeySet
NavigableSet nevigableSet
= geeks.descendingKeySet();
System.out.println("Reverse key values:- "
+ navigableSet);
}
}
Output:
TreeMap values :- {1=Guru, 2=Ayush, 3=Devesh, 4=Kashish}
Reverse key values:- [4, 3, 2, 1]