Java ConcurrentLinkedQueue Class

ConcurrentLinkedQueue is an unbounded thread-safe queue which arranges the element in FIFO. New elements are added at the tail of this queue and the elements are added from the head of this queue.

ConcurrentLinkedQueue class and its iterator implements all the optional methods of the Queue and Iterator interfaces.

Methods

Methods	Description
add()	Inserts the specified element at the tail of this queue
addAll()	Inserts all the elements which are present in the specified collection to the tail of this queue
contains()	Returns true if this queue contains the specified element
forEach()	Performs the given action for each element until all elements have been processed.
isEmpty()	Returns true if this queue contains no elements.
iterator()	Returns an iterator over the elements in this queue
offer()	Inserts the specified element at the tail of this queue
remove()	Removes the specified element from this queue, if this element is present in the queue
removeAll()	Removes all the elements of this in queue which are present in the specified collection.
removeIf()	Removes all the elements in this queue that satisfy the given predicate filter.
retainAll()	Retain only those elements in this queue that are present in the specified collection.
size()	Returns the number of the elements in this queue.
spliterator()	Returns a spliterator over the elements in this queue.
toArray()	Returns an array containing all the elements of this queue which are in proper sequence.

Example 1

import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaConcurrentLinkedQueueExample1 {
    public static void main(String[] args) {
        int j =1;
        ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>();
        for (int i = 1; i <=5; i++) {
            //  Adding items to the tail of this queue
            queue.add(i);}
            //inserts the element at the tail of this queue
            queue.offer(6);
            System.out.println("Queue : "+queue);
            //Returns true if this queue contains the specified element
            if(queue.contains(4)){
                System.out.println("This queue conatins 4");
            }
            else{
                System.out.println("4 is absent");
            }
        //returns true if the queue is empty
        if(queue.isEmpty()){
            System.out.println("Add some elements because the queue is empty.");
        }
        else{
            System.out.println("Queue is not empty");
        }
    }
}

Test it Now

Output:

Queue : [1, 2, 3, 4, 5, 6]
This queue conatins 4
Queue is not empty

Example 2

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaConcurrentLinkedQueueExample2 {
    public static void main(String[] args) {
       ConcurrentLinkedQueue<Integer> queue = new ConcurrentLinkedQueue<Integer>();
       List<Integer> list = new ArrayList<Integer>();
       queue.add(11);
       queue.add(100);
       queue.add(122);
       queue.add(102);
       queue.add(112);
       list.add(11);
       list.add(100);
       System.out.println("Elements in queue : "+queue);
       //remove() method will remove the specified element from the queue
       queue.remove(122);
       queue.remove(102);
       System.out.println("Remaining elements in queue : "+queue);
       //Removes all the elements of this in queue which are present in the list
       queue.removeAll(list);
       System.out.println("Elemts of the list will get removed : "+queue);
       //Retain only those elements in this queue that are present in the list
       queue.retainAll(list);
       System.out.println("Queue will retain the elements of the list: "+queue);
      }
}

Test it Now

Output:

Elements in queue : [11, 100, 122, 102, 112]
Remaining elements in queue : [11, 100, 112]
Elemts of the list will get removed : [112]
Queue will retain the elements of the list: []

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