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Java TreeSet pollFirst() Method with Example

TreeSet Class pollFirst() method: Here, we are going to learn about the pollFirst() method of TreeSet Class with its syntax and example.
Submitted by Preeti Jain, on February 20, 2020

TreeSet Class pollFirst() method

• pollFirst() method is available in java.util package.
• pollFirst() method is used to return the first least element and then remove the first element from this TreeSet.
• pollFirst() 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.

Syntax:

    public Element pollFirst();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of the method is Element, it returns the beginning or first element in this TreeSet otherwise it returns null when this TreeSet holds "none" elements.

Example:

// Java program to demonstrate the example 
// of Element pollFirst() method of TreeSet 

import java.util.*;

public class PollFirstOfTreeSet {
    public static void main(String[] args) {
        // Instantiates a TreeSet object
        TreeSet < String > tree_set = new TreeSet < String > ();

        // By using add() method is to add
        // the given object of this TreeSet 
        tree_set.add("C");
        tree_set.add("C++");
        tree_set.add("JAVA");
        tree_set.add("PHP");
        tree_set.add("SFDC");

        // Display TreeSet
        System.out.println("TreeSet: " + tree_set);

        // By using pollFirst() method is to return
        // the first lowest element and then remove
        // the element exists from this TreeSet
        Object first_lowest = tree_set.pollFirst();

        // Display first_lowest
        System.out.println("tree_set.pollFirst(): " + first_lowest);

        // Display Modified TreeSet
        System.out.println("Modified TreeSet: " + tree_set);
    }
}

Output

TreeSet: [C, C++, JAVA, PHP, SFDC]
tree_set.pollFirst(): C
Modified TreeSet: [C++, JAVA, PHP, SFDC]