java.util.TreeSet.pollFirst() Method

Description

The pollFirst() method is used to retrieve and remove the first (lowest) element, or returns null if this set is empty.

Declaration

Following is the declaration for java.util.TreeSet.pollFirst() method.

public E pollFirst()

Parameters

• NA

Return Value

The method call returns the first element, or null if this set is empty.

Exception

• NA

Example

The following example shows the usage of java.util.TreeSet.pollFirst() method.

package com.tutorialspoint;

import java.util.Iterator;
import java.util.TreeSet;

public class TreeSetDemo {
   public static void main(String[] args) {
      // creating a TreeSet 
      TreeSet <Integer>treeadd = new TreeSet<Integer>();
     
      // adding in the tree set
      treeadd.add(1);
      treeadd.add(13);
      treeadd.add(17);
      treeadd.add(2);
     
      // retrieve and remove the first element
      System.out.println("First element is: "+treeadd.pollFirst());
      
      // create iterator
      Iterator iterator;
      iterator = treeadd.iterator();
     
      // displaying the Tree set data
      System.out.println("Tree set data after removing: ");     
      while (iterator.hasNext()){
         System.out.println(iterator.next() + " ");
      }
   }     
}

Let us compile and run the above program, this will produce the following result.

First element is: 1
Tree set data after removing: 
2 
13 
17