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Java TreeMap descendingMap() Method with Example

TreeMap Class descendingMap() method: Here, we are going to learn about the descendingMap() method of TreeMap Class with its syntax and example.
Submitted by Preeti Jain, on February 19, 2020

TreeMap Class descendingMap() method

• descendingMap() method is available in java.util package.
• descendingMap() method is used to be viewed in reverse order of the mappings (i.e. key-value pairs) that exist in this TreeMap.
• descendingMap() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• descendingMap() method does not throw an exception at the time of returning navigable map.

Syntax:

    public NavigableMap descendingMap();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of the method is NavigableMap, it gets mappings exists in this TreeMap to be viewed in reverse order.

Example:

// Java program to demonstrate the example 
// of NavigableMap descendingMap() method of TreeMap

import java.util.*;

public class DescendingMapOfTreeMap {
    public static void main(String[] args) {
        // Instantiates a TreeMap object
        TreeMap < Integer, String > tree_map = new TreeMap < Integer, String > ();

        // By using put() method is to add
        // key-value pairs in a TreeMap
        tree_map.put(10, "C");
        tree_map.put(20, "C++");
        tree_map.put(50, "JAVA");
        tree_map.put(40, "PHP");
        tree_map.put(30, "SFDC");

        // Display TreeMap 
        System.out.println("TreeMap: " + tree_map);

        // By using descendingMap() method is to
        // order the keys-value pairs in descending order 
        // based on the keys to be viewed in a NavigableMap
        NavigableMap nm = tree_map.descendingMap();

        // Display Status
        System.out.println("tree_map.descendingMap(): " + nm);
    }
}

Output

TreeMap: {10=C, 20=C++, 30=SFDC, 40=PHP, 50=JAVA}
tree_map.descendingMap(): {50=JAVA, 40=PHP, 30=SFDC, 20=C++, 10=C}