BlockingDeque offerFirst() method in Java with Examples

Last Updated : 25 Jan, 2021

The offerFirst(E e) method of BlockingDeque inserts the element passed in the parameter at the front of the Deque container. If the container’s capacity has exceeded, then it does not returns an exception as in case of add() and addFirst() function.

Syntax:

public boolean offerFirst(E e)

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

Returns: This method returns true if the element has been inserted, else it returns false.

Note: The offerFirst() method of BlockingDeque has been inherited from the LinkedBlockingDeque class in Java.

Below programs illustrate offerFirst() method of LinkedBlockingDeque:

Program 1:

Java

// Java Program Demonstrate offerFirst()
// method of BlockingDeque
 
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>(4);
 
        // Add numbers to end of BlockingDeque
        BD.offerFirst(7855642);
        BD.offerFirst(35658786);
        BD.offerFirst(5278367);
        BD.offerFirst(74381793);
 
        // Cannot be inserted
        BD.offerFirst(10);
 
        // cannot be inserted hence returns false
        if (!BD.offerFirst(10))
            System.out.println("The element 10 cannot be inserted"
                               + " as capacity is full");
 
        // before removing print queue
        System.out.println("Blocking Deque: " + BD);
    }
}

Output:

The element 10 cannot be inserted as capacity is full
Blocking Deque: [74381793, 5278367, 35658786, 7855642]

Program 2:

Java

// Java Program Demonstrate offerFirst()
// method of BlockingDeque
 
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
        throws IllegalStateException
    {
 
        // create object of BlockingDeque
        BlockingDeque<String> BD
            = new LinkedBlockingDeque<String>(4);
 
        // Add numbers to end of BlockingDeque
        BD.offerFirst("abc");
        BD.offerFirst("gopu");
        BD.offerFirst("geeks");
        BD.offerFirst("richik");
 
        // Cannot be inserted
        BD.offerFirst("hii");
 
        // cannot be inserted hence returns false
        if (!BD.offerFirst("hii"))
            System.out.println("The element 'hii' cannot be"
                               + " inserted as capacity is full");
 
        // before removing print queue
        System.out.println("Blocking Deque: " + BD);
    }
}

Output:

The element 'hii' cannot be inserted as capacity is full
Blocking Deque: [richik, geeks, gopu, abc]

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#offerFirst(E)

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