LinkedBlockingQueue iterator() method in Java

Last Updated : 13 Jul, 2021

The iterator() method of LinkedBlockingQueue returns an iterator of the same elements, as this LinkedBlockingQueue, in a proper sequence. The elements returned from this method contains all the elements in order from first(head) to last(tail) of LinkedBlockingQueue. The returned iterator is weakly consistent.
Syntax:

public Iterator<E> iterator()

Return Value: The method returns the iterator having same elements as present in LinkedBlockingQueue in order from first(head) to last(tail).
Below programs illustrates iterator() method of LinkedBlockingQueue class:
Program 1: Creating an Iterator from LinkedBlockingQueue which contains names of different student of a class.

Java

// Java Program Demonstrate iterator()
// method of LinkedBlockingQueue

import java.util.concurrent.LinkedBlockingQueue;
import java.util.Iterator;

public class GFG {

    public static void main(String[] args)
    {
        // define capacity of LinkedBlockingQueue
        int capacityOfQueue = 7;

        // create object of LinkedBlockingQueue
        LinkedBlockingQueue<String> linkedQueue
            = new LinkedBlockingQueue<String>(capacityOfQueue);

        // Add element to LinkedBlockingQueue
        linkedQueue.add("John");
        linkedQueue.add("Tom");
        linkedQueue.add("Clark");
        linkedQueue.add("Kat");

        // create Iterator of linkedQueue using iterator() method
        Iterator<String> listOfNames = linkedQueue.iterator();

        // print result
        System.out.println("list of names:");
        while (listOfNames.hasNext())
            System.out.println(listOfNames.next());
    }
}

Output:

list of names:
John
Tom
Clark
Kat

Program 2: Creating an Iterator from LinkedBlockingQueue which contains list of Employees.

Java

// Java Program Demonstrate iterator()
// method of LinkedBlockingQueue

import java.util.concurrent.LinkedBlockingQueue;
import java.util.Iterator;

public class GFG {

    public void collectIterator()
    {
        // define capacity of LinkedBlockingQueue
        int capacityOfQueue = 7;

        // create object of LinkedBlockingQueue
        LinkedBlockingQueue<Employee> linkedQueue
            = new LinkedBlockingQueue<Employee>(capacityOfQueue);

        // Add element to LinkedBlockingQueue
        Employee emp1 = new Employee("Sachin", "Developer", "39000");
        Employee emp2 = new Employee("Sanjeev", "Tester", "26000");

        // Add Employee Objects to linkedQueue
        linkedQueue.add(emp1);
        linkedQueue.add(emp2);

        // create Iterator of linkedQueue using iterator() method
        Iterator<Employee> listOfEmployee = linkedQueue.iterator();

        // print result from iterator
        System.out.println("list of Employees:");
        while (listOfEmployee.hasNext()) {
            System.out.println("*************************");
            Employee emp = listOfEmployee.next();
            System.out.println("Employee Name : " + emp.name);
            System.out.println("Employee Position : " + emp.position);
            System.out.println("Employee Salary : " + emp.salary);
        }
    }

    // create an Employee Object with name,
    // position and salary as an attribute
    public class Employee {

        public String name;
        public String position;
        public String salary;

        Employee(String name, String position, String salary)
        {
            this.name = name;
            this.position = position;
            this.salary = salary;
        }

        @Override
        public String toString()
        {
            return "Employee [name=" + name + ", position="
                + position + ", salary=" + salary + "]";
        }
    }

    // Main Method
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        gfg.collectIterator();
    }
}

Output:

list of Employees:
*************************
Employee Name : Sachin
Employee Position : Developer
Employee Salary : 39000
*************************
Employee Name : Sanjeev
Employee Position : Tester
Employee Salary : 26000

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/LinkedBlockingQueue.html#iterator--

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