LinkedBlockingDeque putFirst() method in Java

The putFirst(E e) method of LinkedBlockingDeque inserts the specified element at the front of the queue represented by this deque. If the Deque is capacity restricted, then it will wait for the space to become available.

Syntax:

public void putFirst(E e)

Parameters: This method accepts a mandatory parameter e which is the element to be inserted at the front of the LinkedBlockingDeque.

Returns: This method does not return anything.

Exceptions: The program throws two exceptions as shown below:

• NullPointerException – if the specified element is null
• InterruptedException – if interrupted while waiting

Below programs illustrate putFirst() method of LinkedBlockingDeque:

Program 1:

// Java Program Demonstrate putFirst()
// 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.putFirst(7855642);
        LBD.putFirst(35658786);
        LBD.putFirst(5278367);
        LBD.putFirst(74381793);

        // print Dequeue
        System.out.println("Linked Blocking Deque: " + LBD);
    }
}

Output:

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

Program 2:

// Java Program Demonstrate putFirst()
// method of LinkedBlockingDeque
// throwing NullPointerException

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.putFirst(7855642);
        LBD.putFirst(35658786);
        LBD.putFirst(5278367);

        // throws an exception
        LBD.putFirst(null);

        // print Dequeue
        System.out.println("Linked Blocking Deque: " + LBD);
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
    at java.util.concurrent.LinkedBlockingDeque.putFirst(LinkedBlockingDeque.java:373)
    at GFG.main(GFG.java:23)

Program 3:

// Java Program Demonstrate putFirst()
// method of LinkedBlockingDeque
// when capacity exceeded

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>(3);

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

        // throws an exception
        LBD.putFirst(4356789);

        // print Dequeue
        System.out.println("Linked Blocking Deque: " + LBD);
    }
}

Output:

Runtime Errors:
Max real time limit exceeded due to either by
heavy load on server or by using sleep function

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/LinkedBlockingDeque.html#putFirst-E-