NavigableSet pollFirst() method in Java

The pollFirst() method of NavigableSet interface in Java is used to retrieves and removes the first (lowest) element, or returns null if this set is empty.

Syntax:

E pollFirst()

Where, E is the type of elements maintained by this Set container.



Parameters: This function does not accepts any parameter.

Return Value: It returns returns null if this set is empty.

Below programs illustrate the pollFirst() method in Java:

Program 1: NavigableSet with integer elements.

filter_none

edit
close

play_arrow

link
brightness_4
code

// A Java program to demonstrate
// pollFirst() method of NavigableSet
  
import java.util.NavigableSet;
import java.util.TreeSet;
  
public class GFG {
    public static void main(String[] args)
    {
        NavigableSet<Integer> ns = new TreeSet<>();
        ns.add(0);
        ns.add(1);
        ns.add(2);
        ns.add(3);
        ns.add(4);
        ns.add(5);
        ns.add(6);
  
        System.out.println("First lowest element removed is : " 
                                              + ns.pollFirst());
    }
}

chevron_right


Output:

First lowest element removed is : 0

Program 2: NavigableSet with string elements.

filter_none

edit
close

play_arrow

link
brightness_4
code

// A Java program to demonstrate
// pollFirst() method of NavigableSet
  
import java.util.NavigableSet;
import java.util.TreeSet;
  
public class GFG {
    public static void main(String[] args)
    {
        NavigableSet<String> ns = new TreeSet<>();
        ns.add("A");
        ns.add("B");
        ns.add("C");
        ns.add("D");
        ns.add("E");
        ns.add("F");
        ns.add("G");
  
        System.out.println("First lowest element removed is : " 
                                              + ns.pollFirst());
    }
}

chevron_right


Output:

First lowest element removed is : A

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/NavigableSet.html#pollFirst(E)



My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.