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#Enqueue dequeue java example full#
#Enqueue dequeue java example code#
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This method takes an element from the head of the queue, provided the queue is not empty. If, on the other hand, the waiting time expires without any space being freed, the method returns false. If a space becomes available during this time, the element is inserted, and the method returns true. Otherwise, the method waits for the specified time. BlockingQueue.offer() with TimeoutĪlso, the offer() method inserts an element if there is still space in the queue. However, if the queue's capacity limit is reached, the method blocks until space is freed.

The put() method inserts an element into the queue if space is available. BlockingQueue Methods BlockingQueue.put()

The following section describes the BlockingQueue methods in detail.

In the third and fourth columns, you will find the added blocking methods: In the first two columns, the following table shows the non-blocking methods that BlockingQueue inherits from Queue (and that we discussed in the previous part of the tutorial). The second variant gives up after a specified waiting time and returns false or null. The blocking enqueue and dequeue operations each come in two variants. As a rule, it is not necessary to activate the fairness policy. However, this increases the overhead and thus massively reduces the throughput of the queue. You can activate the processing in call order in some queue implementations through an optional "fairness policy". Fairness Policyīlocking methods are not automatically processed in the order they were called. I will explain them in the following chapter. These additional methods are defined in the BlockingQueue interface.

Dequeue methods that, when taking an element from an empty queue, wait for the queue to become non-empty (this requires another thread to insert an element).

#Enqueue dequeue java example full#

Enqueue methods that, when inserting into a full bounded queue, wait until the queue has free capacity again (this requires another thread to take an element).

We could try to take an element from an empty queue.Ī non-blocking queue returns a specific return value or throws an exception in such cases (see section "Queue Methods" in the article about Java queues).Ī blocking queue, on the other hand, provides additional methods that wait for the desired operation to be executed:.

We could try to insert an element into a bounded queue that has reached its capacity limit – in other words, that is full.

Two special cases can occur with the "Enqueue" and "Dequeue" queue operations: (By the way, the same definition applies to all data structures, e.g., also to stacks and deques.) What Is a Blocking Queue? IOn the other hand, if the number of elements in the queue is not limited (or is limited only by the available memory), we speak of an "unbounded queue".

#Enqueue dequeue java example code#

The maximum number of elements is referred to as "capacity" and is specified when the queue is created.įor example, the following line of code creates an ArrayBlockingQueue limited to 100 elements: Queue queue = new ArrayBlockingQueue( 100) Code language: Java ( java ) If a queue can only hold a limited number of elements, it is referred to as a "bounded queue".

#Enqueue dequeue java example series#

BlockingQueue extends Java's Queue interface discussed in the previous part of this tutorial series with methods for blocking access.īefore we clarify what "blocking access" means, we first need to talk about the term "bounded queue". In this article, you will learn about the interface.