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Showing content from https://www.geeksforgeeks.org/java/queue-peek-method-in-java/ below:

Queue peek() method in Java

Last Updated : 11 Jul, 2025

The

peek()

method of

Queue Interface

returns the element at the front the container. It does not deletes the element in the container. This method returns the head of the queue. The method does not throws an exception when the Queue is empty, it returns

null

instead.

Syntax:

E peek()

Returns:

This method returns the

head

of the Queue, it returns false when the Queue is empty Below programs illustrate peek() method of Queue:

Program 1:

With the help of

LinkedList

Java


 // Java Program Demonstrate peek()
// 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
        System.out.println("Queue's head: " + Q.peek());

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

Output:

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

Program 2:

To demonstrate peek() method of Queue when Queue is empty

Java


 // Java Program Demonstrate peek()
// method of Queue when Queue is empty

import java.util.*;

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

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

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

        // print head
        System.out.println("Queue's head: " + Q.peek());
    }
}

Output:

Queue: []
Queue's head: null

Program 3:

With the help of

ArrayDeque

Java


 // Java Program Demonstrate peek()
// 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
        System.out.println("Queue's head: " + Q.peek());
    }
}

Output:

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

Program 4:

With the help of

LinkedBlockingDeque

Java


 // Java Program Demonstrate peek()
// 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
        System.out.println("Queue's head: " + Q.peek());
    }
}

Output:

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

Program 5:

With the help of

ConcurrentLinkedDeque

Java


 // Java Program Demonstrate peek()
// 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
        System.out.println("Queue's head: " + Q.peek());
    }
}

Output:

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

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

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