Queue remove() method in Java

The remove() method of Queue Interface returns and removes the element at the front of the container. It deletes the head of the container. The method throws an NoSuchElementException when the Queue is empty. 

Syntax:

E remove()

Returns: This method returns the head of the Queue. 

Exception: The function throws an NoSuchElementException when the Queue is empty. 

Below programs illustrate remove() method of Queue: 

Program 1: With the help of LinkedList. 

Java

// Java Program Demonstrate remove()
// method of Queue

import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of Queue
        Queue<Integer> Q
            = new LinkedList<Integer>();

        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);

        // print queue
        System.out.println("Queue: " + Q);

        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());

        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

Output:

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

Program 2: With the help of ArrayDeque. 

Java

// Java Program Demonstrate remove()
// method of Queue

import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of Queue
        Queue<Integer> Q
            = new ArrayDeque<Integer>();

        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);

        // print queue
        System.out.println("Queue: " + Q);

        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());

        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

Output:

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

Program 3: With the help of LinkedBlockingDeque. 

Java

// Java Program Demonstrate remove()
// method of Queue

import java.util.*;
import java.util.concurrent.LinkedBlockingDeque;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of Queue
        Queue<Integer> Q
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);

        // print queue
        System.out.println("Queue: " + Q);

        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());

        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

Output:

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

Program 4: With the help of ConcurrentLinkedDeque. 

Java

// Java Program Demonstrate remove()
// method of Queue

import java.util.*;
import java.util.concurrent.ConcurrentLinkedDeque;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of Queue
        Queue<Integer> Q
            = new ConcurrentLinkedDeque<Integer>();

        // Add numbers to end of Queue
        Q.add(7855642);
        Q.add(35658786);
        Q.add(5278367);
        Q.add(74381793);

        // print queue
        System.out.println("Queue: " + Q);

        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());

        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());
    }
}

Output:

Queue: [7855642, 35658786, 5278367, 74381793]
Queue's head: 7855642
Queue's head: 35658786

Below programs illustrate exceptions thrown by this method: Program 5: To show NoSuchElementException. 

Java

// Java Program Demonstrate remove()
// method of Queue

import java.util.*;

public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {

        // create object of Queue
        Queue<Integer> Q
            = new LinkedList<Integer>();

        // Add numbers to end of Queue
        Q.add(423);
        Q.add(3432);

        // print queue
        System.out.println("Queue: " + Q);

        // print head and deletes the head
        System.out.println("Queue's head: " + Q.remove());

        // print head and deleted the head
        System.out.println("Queue's head: " + Q.remove());

        // print queue
        System.out.println("Queue: " + Q);

        try {
            // Queue is empty now hence exception
            System.out.println("Queue's head: " + Q.element());
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Queue: [423, 3432]
Queue's head: 423
Queue's head: 3432
Queue: []
Exception: java.util.NoSuchElementException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html#remove–