SortedMap firstKey() method in Java

The firstKey() method of SortedMap interface in Java is used to return the first or the lowest key currently in this map.

Syntax:

K firstKey()

Where, K is the type of key maintained by this Set.

Parameters: This function does not accepts any parameter.

Return Value: It returns the first print the lowest key currently in this map

Exception: It throws NoSuchElementException, if this map is empty.

Below programs illustrate the above method:

Program 1:

// A Java program to demonstrate 
// working of SortedMap 
import java.util.*; 
  
public class Main { 
    public static void main(String[] args) 
    { 
        // Create a TreeMap of SortedMap 
        SortedMap<Integer, String> mp = new TreeMap<>(); 
  
        // Adding Element to SortedSet 
        mp.put(1, "One"); 
        mp.put(5, "Five"); 
        mp.put(2, "Two"); 
        mp.put(3, "Three"); 
        mp.put(9, "Nine"); 
  
        // Returning the first key element 
        // from the map 
        System.out.print("First Key in the map : "
                         + mp.firstKey()); 
    } 
} 

Output:

First Key in the map : 1

Program 2:

// A Java program to demonstrate 
// working of SortedSet 
import java.util.*; 
  
public class Main { 
    public static void main(String[] args) 
    { 
        // Create a TreeSet and inserting elements 
        SortedMap<String, String> mp = new TreeMap<>(); 
  
        // Adding Element to SortedSet 
        mp.put("One", "Beginner"); 
        mp.put("Two", "For"); 
        mp.put("Three", "Beginner"); 
        mp.put("Four", "Code"); 
        mp.put("Five", "It"); 
  
        // Returning the first key 
        // from the map 
        System.out.print("First Key in the map is : "
                         + mp.firstKey()); 
    } 
} 

Output:

First Key in the map is : Five

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/SortedMap.html#firstKey()

Tags:

#Java - util package #Java-Collections #Java-Functions #Java-SortedMap #Java #Java #Java-Collections

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