The poll(long timeout, TimeUnit unit) method of BlockingQueue interface returns the head of BlockingQueue by removing that element from the queue. It can be said that this method retrieves and removes element from head of this LinkedBlockingQueue. If queue is empty, then poll() method will wait till a specified time for an element to become available.
Syntax:
public E poll(long timeout, TimeUnit unit) throws
Parameters: This method takes two mandatory parameters:
- timeout– how long to wait, in units of unit.
- unit– a TimeUnit for the timeout parameter.
Return Value: This method retrieves and removes element from head of this LinkedBlockingQueue, or null if the specified waiting time elapses before an element is available.
Exception This method throws InterruptedException if method interrupted while waiting for an element to become available.
Note: The poll() method of BlockingQueue has been inherited from the Queue class in Java.
Below programs illustrates poll(long timeout, TimeUnit unit) method of BlockingQueue:
Program 1:
// Java program to demonstrate// poll(long timeout, TimeUnit unit)// method of LinkedBlockingQueue import java.util.concurrent.LinkedBlockingQueue;import java.util.concurrent.BlockingQueue;import java.util.concurrent.TimeUnit; public class GFG { public static void main(String[] args) throws InterruptedException { // define capacity of BlockingQueue int capacityOfQueue = 4; // create object of BlockingQueue BlockingQueue<String> BQ = new LinkedBlockingQueue<String>(capacityOfQueue); // Add element to BlockingQueue BQ.add("Ravi"); BQ.add("Suraj"); BQ.add("Harsh"); // print elements of queue System.out.println("Items in Queue are " + BQ); // Try to poll elements from BQ // using poll(long timeout, TimeUnit unit) method System.out.println("Removing item From head: " + BQ.poll(5, TimeUnit.SECONDS)); // print queue details System.out.println("Now Queue Contains" + BQ); // using poll(long timeout, TimeUnit unit) method System.out.println("Removing item From head: " + BQ.poll(5, TimeUnit.SECONDS)); // print queue details System.out.println("Now Queue Contains" + BQ); // using poll(long timeout, TimeUnit unit) method System.out.println("Removing item From head: " + BQ.poll(5, TimeUnit.SECONDS)); // print queue details System.out.println("Now Queue Contains" + BQ); // using poll(long timeout, TimeUnit unit) method System.out.println("Removing item From head: " + BQ.poll(5, TimeUnit.SECONDS)); // print queue details System.out.println("Now Queue Contains" + BQ); }} |
Items in Queue are [Ravi, Suraj, Harsh] Removing item From head: Ravi Now Queue Contains[Suraj, Harsh] Removing item From head: Suraj Now Queue Contains[Harsh] Removing item From head: Harsh Now Queue Contains[] Removing item From head: null Now Queue Contains[]
Program 2:
// Java program to demonstrate// poll(long timeout, TimeUnit unit)// method of LinkedBlockingQueue import java.util.concurrent.LinkedBlockingQueue;import java.util.concurrent.BlockingQueue;import java.util.concurrent.TimeUnit; public class GFG { public static void main(String[] args) throws InterruptedException { // define capacity of BlockingQueue int capacityOfQueue = 2; // create object of BlockingQueue BlockingQueue<String> BQ = new LinkedBlockingQueue<String>(capacityOfQueue); // Add element to BlockingQueue BQ.add("Gopal"); BQ.add("GFG"); // print elements of queue System.out.println("Items in Queue are " + BQ); // Try to poll elements from BQ // using poll(long timeout, TimeUnit unit) method System.out.println("Removing item From head: " + BQ.poll(2, TimeUnit.SECONDS)); // print queue details System.out.println("Now Queue Contains" + BQ); }} |
Items in Queue are [Gopal, GFG] Removing item From head: Gopal Now Queue Contains[GFG]
