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LinkedBlockingDeque peek() method in Java

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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()

Last Updated : 14 Sep, 2018
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