LinkedBlockingDeque peek() method in Java

The peek() method of LinkedBlockingDeque returns the front element in the Deque container. It returns null if the container is empty.

Syntax:

public E peek()

Parameters: This method does not accept any parameters.

Returns: This method returns front element in the Deque container if the container is not empty. It returns false if the container is empty.

Below programs illustrate peek() method of LinkedBlockingDeque:

Program 1:

// Java Program Demonstrate peek()
// method of LinkedBlockingDeque

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

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

    {

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

        // Add numbers to end of LinkedBlockingDeque
        LBD.add(7855642);
        LBD.add(35658786);
        LBD.add(5278367);
        LBD.add(74381793);

        // Print the queue
        System.out.println("Linked Blocking Deque: " + LBD);

        System.out.println("Front element in Deque: " + LBD.peek());
    }
}

Output:

Linked Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: 7855642

Program 2:

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

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

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

    {

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

        // Add numbers to end of LinkedBlockingDeque
        LBD.add(7855642);
        LBD.add(35658786);
        LBD.add(5278367);
        LBD.add(74381793);

        // Print the queue
        System.out.println("Linked Blocking Deque: " + LBD);

        // empty deque
        LBD.clear();

        System.out.println("Front element in Deque: " + LBD.peek());
    }
}

Output:

Linked Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: null

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#peek()