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CLEAR QUEUE JAVA CODE

TransferQueue is a specialized BlockingQueue in which code that adds an element to the queue has the option of waiting (blocking) for code in another thread to retrieve the element. The key classes and interfaces are: Channel: represents an AMQP 0-9-1 channel, and provides most of the operations (protocol methods).

RabbitMQ Java client uses as its top-level package.

SynchronousQueue a simple rendezvous mechanism that uses the BlockingQueue interface The client API exposes key entities in the AMQP 0-9-1 protocol model, with additional abstractions for ease of use.

DelayQueue a time-based scheduling queue backed by a heap.

PriorityBlockingQueue an unbounded blocking priority queue backed by a heap.

ArrayBlockingQueue a bounded FIFO blocking queue backed by an array.

LinkedBlockingQueue an optionally bounded FIFO blocking queue backed by linked nodes.

The tail of the queue is that element that. The head of the queue is that element that has been on the queue the longest time. This queue orders elements FIFO (first-in-first-out). An optionally-bounded blocking queue based on linked nodes.

From lines 8 to 11, we call the isEmpty() method to check whether the PriorityQueue is empty or not and display the message accordingly. public class LinkedBlockingQueue extends AbstractQueue implements BlockingQueue , Serializable.

In line 6, we declare a PriorityQueue that consists of integer type elements. This interface is implemented by the following classes: In line 1, we import the required package.

The package contains a set of synchronized Queue interfaces and classes.īlockingQueue extends Queue with operations that wait for the queue to become nonempty when retrieving an element and for space to become available in the queue when storing an element. For ordered traversal, consider using Arrays.sort(pq.toArray()). The iterator provided in method iterator is not guaranteed to traverse the elements of the PriorityQueue in any particular order. PriorityQueue and its iterator implement all of the optional methods of the Collection and Iterator interfaces. If multiple elements are tied for least value, the head is one of those elements ties are broken arbitrarily. The head of the queue is the least element with respect to the specified ordering. The queue retrieval operations poll, remove, peek, and element access the element at the head of the queue. This queue orders elements according to the order specified at construction time, which can be the elements' natural ordering or the ordering imposed by an explicit Comparator. PriorityQueue class is a priority queue based on the heap data structure. General-Purpose Queue ImplementationsĪs mentioned in the previous section, LinkedList implements the Queue interface, providing first in, first out (FIFO) queue operations for add, poll, and so on. The consumer will wait on the countDownLatch using the await() method.The Queue implementations are grouped into general-purpose and concurrent implementations. Integer producedElement = ThreadLocalRandom The producer will save a random integer to the sharedState variable, and execute the countDown() method on the countDownLatch, signaling to the consumer that it can fetch a value from the sharedState: We will define a sharedState variable and a CountDownLatch that will be used for coordinating processing: ExecutorService executor = Executors.newFixedThreadPool(2) ĪtomicInteger sharedState = new AtomicInteger() ĬountDownLatch countDownLatch = new CountDownLatch(1) We will use the CountDownLatch to coordinate those two threads, to prevent a situation when the consumer accesses a value of a shared variable that was not set yet. Most Deque implementations place no fixed limits on the number of elements they may contain, but this interface supports capacity-restricted. The name deque is short for 'double ended queue' and is usually pronounced 'deck'. A linear collection that supports element insertion and removal at both ends.

Next, the consumer thread will fetch a value from a shared variable. public interface Deque extends Queue .

Let’s say that we have two threads – a producer and a consumer – and when the producer is setting a value of a shared variable, we want to signal that fact to the consumer thread. To see why the SynchronousQueue can be so useful, we will implement a logic using a shared variable between two threads and next, we will rewrite that logic using SynchronousQueue making our code a lot simpler and more readable.