LinkedBlockingDeque removeFirst() method in Java

The removeFirst() method of LinkedBlockingDeque returns and removes the first element of the Deque container from it. The method throws an NoSuchElementException if the Deque container is empty.

Syntax:

public E removeFirst()

Returns: This method returns the head of the Deque container, which is the first element.

Exception: The function throws a NoSuchElementException if the Deque is empty.

Below programs illustrate removeFirst() method of LinkedBlockingDeque:

Program 1:

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// Java Program to demonstrate removeFirst()
// method of LinkedBlockingDeque
  
import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
        throws InterruptedException
    {
  
        // 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 Dequee
        System.out.println("Linked Blocking Deque: " + LBD);
  
        // removes the front element and prints it
        System.out.println("First element of Linked Blocking Deque: "
                           + LBD.removeFirst());
  
        // prints the Deque
        System.out.println("Linked Blocking Deque: " + LBD);
    }
}

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Output:

Linked Blocking Deque: [7855642, 35658786, 5278367, 74381793]

First element of Linked Blocking Deque: 7855642

Linked Blocking Deque: [35658786, 5278367, 74381793]

Program 2:

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// Java Program to demonstrate removeFirst()
// method of LinkedBlockingDeque
  
import java.util.concurrent.LinkedBlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
        throws NoSuchElementException
    {
  
        // create object of LinkedBlockingDeque
        LinkedBlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>();
  
        // print Dequee
        System.out.println("Linked Blocking Deque: " + LBD);
  
        try {
            // throws an exception
            LBD.removeFirst();
        }
        catch (Exception e) {
            System.out.println("Exception when removing "
                               + "first element from this Deque: "
                               + e);
        }
    }
}

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Output:

Linked Blocking Deque: []
Exception when removing first element from this Deque: java.util.NoSuchElementException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/LinkedBlockingDeque.html#removeFirst–



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