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BlockingDeque push() method in Java with examples
  • Last Updated : 26 Jan, 2021

The push(E e) method of BlockingDeque pushes an element onto the stack represented by this deque. It inserts the element passed in the parameter to the front of the Deque if there is space. If the BlockingDeque is capacity restricted and no space is left for insertion, it returns an IllegalStateException. This function is similar to that of addFirst().

Syntax:  

public void push(E e)

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

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

Returns: This method does not return anything. 



Exception:  

  • IllegalStateException: if the element cannot be added at this time due to capacity restrictions
  • NullPointerException: if the specified element is null

Below programs illustrate push() method of BlockingDeque:

Program 1:  

Java




// Java Program Demonstrate push()
// 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>();
 
        // Add numbers to end of BlockingDeque
        BD.push(7855642);
        BD.push(35658786);
        BD.push(5278367);
        BD.push(74381793);
 
        // before removing print queue
        System.out.println("Blocking Deque: " + BD);
    }
}


Output: 

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

 

Program 2: 

Java




// Java Program Demonstrate push()
// method of BlockingDeque
// when it is Full
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
        // size of list
        BlockingDeque<Integer> LBD
            = new LinkedBlockingDeque<Integer>(3);
 
        // Add numbers to end of BlockingDeque
        BD.push(7855642);
        BD.push(35658786);
        BD.push(5278367);
 
        // it is full
        BD.push(74381793);
 
        // before removing print queue
        System.out.println("Blocking Deque: " + BD);
    }
}


Output: 

Exception in thread "main" java.lang.IllegalStateException: Deque full
    at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:326)
    at java.util.concurrent.LinkedBlockingDeque.push(LinkedBlockingDeque.java:770)
    at GFG.main(GFG.java:24)

Program 3: 

Java




// Java Program Demonstrate push()
// method of BlockingDeque
// when null is inserted
 
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>();
 
        // Add numbers to end of BlockingDeque
        BD.push(7855642);
        BD.push(35658786);
        BD.push(5278367);
 
        // NULL
        BD.push(null);
 
        // before removing print Deque
        System.out.println("Blocking Deque: " + BD);
    }
}


Output: 

Exception in thread "main" java.lang.NullPointerException
    at java.util.concurrent.LinkedBlockingDeque.offerFirst(LinkedBlockingDeque.java:342)
    at java.util.concurrent.LinkedBlockingDeque.addFirst(LinkedBlockingDeque.java:325)
    at java.util.concurrent.LinkedBlockingDeque.push(LinkedBlockingDeque.java:770)
    at GFG.main(GFG.java:24)

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

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