Difference Between poll() and remove() method of Queue Interface in Java

A data structure called a queue holds elements in a first-in, first-out (FIFO) manner. It may be used as a fundamental synchronisation primitive or as a priority queue implementation. The element is taken out of the queue's head by the remove() method, which then returns it. The poll() method waits for one or more elements to become free for removal before returning those elements but keeping all other elements in the queue.

The difference between these two methods is that when you call poll(), it will block until one or more elements become available for removal, then return those elements without removing them from the queue; in contrast, when you call remove(), it removes an element from the head of this queue and returns it right away without blocking if there are no items in your collection.

poll() Method:

The element at the front-end of the container is removed by the poll() method of the Queue Interface and returned. The container's element is removed as a result. When given an empty queue, the method returns null without throwing an exception. The syntax for this method is as follows:

Syntax:

public E poll() throws InterruptedException, ExecutionException;

Implementation:

FileName: PollExample.java

import java.util.Iterator;

import java.util.LinkedList;

import java.util.Queue;

import java.io.*;

public class PollExample

{

   public static void main(String args[])

   {

      Queue queue = new LinkedList();

      // Addition of elements to Queue

      queue.add("C");

      queue.add("C++");

      queue.add("JAVA");

      queue.add("PYTHON");

      queue.add("HTML");

      // prints the front-end element and deletes the front-end element of the queue

      System.out.println("Element at the top of the queue: "+queue.poll());

      Iterator it = queue.iterator();

      // Remaining elements present in the queue are printed

      System.out.println("Remaining Contents present in the queue: ");

      while(it.hasNext())

      {

         System.out.println(it.next());

      }

   }

}

Output:

Element at the top of the queue: C

Remaining Contents present in the queue:

C++

JAVA

PYTHON

HTML

remove() Method:

The oldest element in the queue is eliminated via the remove() method of a Queue interface. If the queue is empty, the remove() method throws an error; otherwise, it gives no results. This method's syntax is as follows:

Syntax:

queue.remove();

Implementation:

FileName: RemoveExample.java

import java.util.Iterator;

import java.util.LinkedList;

import java.util.Queue;

import java.io.*;

public class RemoveExample

{

   public static void main(String args[])

   {

      Queue queue = new LinkedList();

      // Addition of elements to Queue

      queue.add("C++");

      queue.add("Java");

      queue.add("HTML");

      queue.add("C");

      queue.add("PYTHON");

      // prints the oldest element and deletes that oldest element present in the Queue

      System.out.println("Element at the top of the queue: "+queue.remove());

      Iterator it = queue.iterator();

      // Remaining elements present in the queue are printed

      System.out.println("Remaining Contents of the queue: ");

      while(it.hasNext())

      {

         System.out.println(it.next());

      }

   }

}

Output:

Element at the top of the queue: C++

Remaining Contents of the queue:

Java

HTML

C

PYTHON

Comparison between poll() and remove() Methods:

Performance Comparison:

According to their temporal complexity and spatial complexity, the poll() and remove() methods of the Java Queue are compared for performance. It will always take a fixed amount of time to execute the poll() method because its time complexity is O(1). In contrast to other Java methods, there won't be any extra expenses for invoking this one, to put it in a different context.

The complexity of the remove() method, is O(n), where n is the number of elements in the queue at any given time. This means that each time you call remove(), it will take a linear number of operations (O(1)) to remove one item from the queue, making it slower than the poll() method when they are side by side compared.