TreeMap lastKey() Method in Java

The java.util.TreeMap.lastKey() is used to retrieve the last or the highest key present in the map.

Syntax:

 tree_map.lastKey()

Parameters: The method does not take any parameters.

Return Value: The method returns the last key present in the map.

Exception: The method throws NoSuchElementException if the map is empty.

Below programs illustrate the working of java.util.TreeMap.lastKey() method:
Program 1:

// Java code to illustrate the lastKey() method
import java.util.*;

public class Tree_Map_Demo {
    public static void main(String[] args)
    {

        // Creating an empty TreeMap
        TreeMap<Integer, String> tree_map = new TreeMap<Integer, String>();

        // Mapping string values to int keys
        tree_map.put(10, "Geeks");
        tree_map.put(15, "4");
        tree_map.put(20, "Geeks");
        tree_map.put(25, "Welcomes");
        tree_map.put(30, "You");

        // Displaying the TreeMap
        System.out.println("The Mappings are: " + tree_map);

        // Displaying the lastKey of the map
        System.out.println("The last key is " + tree_map.lastKey());
    }
}

Output:

The Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The last key is 30

Program 2:

// Java code to illustrate the lastKey() method
import java.util.*;

public class Tree_Map_Demo {
    public static void main(String[] args)
    {

        // Creating an empty TreeMap
        TreeMap<String, Integer> tree_map = new TreeMap<String, Integer>();

        // Mapping int values to string keys
        tree_map.put("Geeks", 10);
        tree_map.put("4", 15);
        tree_map.put("Geeks", 20);
        tree_map.put("Welcomes", 25);
        tree_map.put("You", 30);

        // Displaying the TreeMap
        System.out.println("The Mappings are: " + tree_map);

        // Displaying the lastKey of the map
        System.out.println("The last key is " + tree_map.lastKey());
    }
}

Output:

The Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
The last key is You