Java Program to Implement LinkedTransferQueue API

LinkedTransferQueue is a queue that orders elements FIFO (first-in-first-out) with respect to any given producer. The head of the queue is that element that has been on the queue the longest time for some producer. The tail of the queue is that element that has been on the queue the shortest time for some producer.

Constructor Summary

1. LinkedTransferQueue​(): Creates an initially empty LinkedTransferQueue.

2. LinkedTransferQueue​(Collection<? extends E> c): Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection’s iterator.

Java

// Java Program to Implement LinkedTransferQueue API

import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.TimeUnit;

public class LinkedTransferQueueImpl<E> {
    private LinkedTransferQueue<E> linkedTransferQueue;

    // Create an empty LinkedTransferQueue
    public LinkedTransferQueueImpl()
    {
        linkedTransferQueue = new LinkedTransferQueue<E>();
    }

    // Creates a LinkedTransferQueue containing
    // the elements of the given collection
    public LinkedTransferQueueImpl(
        Collection<? extends E> c)
    {
        linkedTransferQueue = new LinkedTransferQueue<E>(c);
    }

    // add the given element at the end or tail
    // of queue
    public boolean add(E e)
    {
        return linkedTransferQueue.add(e);
    }

    // remove all the elements from queue
    public void clear() { linkedTransferQueue.clear(); }

    // return true if the given object is present
    public boolean contains(Object o)
    {
        return linkedTransferQueue.contains(o);
    }

    // Returns an estimate of the number of consumers
    // waiting to receive elements via BlockingQueue.take()
    // or timed poll.
    public int getWaitingConsumerCount()
    {
        return linkedTransferQueue
            .getWaitingConsumerCount();
    }

    // Returns true if there is at least one consumer
    // waiting to receive an element via
    // BlockingQueue.take() or timed poll.
    public boolean hasWaitingConsumer()
    {
        return linkedTransferQueue.hasWaitingConsumer();
    }

    // remove all the elements from the queue and add them
    // to the provided Collection
    public int drainTo(Collection<? super E> c)
    {
        return linkedTransferQueue.drainTo(c);
    }

    // Removes at most the given number of available
    // elements from this queue and adds them to the given
    // collection.
    public int drainTo(Collection<? super E> c,
                       int maxElements)
    {
        return linkedTransferQueue.drainTo(c, maxElements);
    }

    // Returns an iterator over the elements in this queue
    // in proper sequence.
    public Iterator<E> iterator()
    {
        return linkedTransferQueue.iterator();
    }

    // Inserts the specified element at the tail of this
    // queue if it is possible to do so immediately without
    // exceeding the queue's capacity, returning true upon
    // success and false if this queue is full.
    public boolean offer(E e)
    {
        return linkedTransferQueue.offer(e);
    }

    // Inserts the specified element at the tail of this
    // queue, waiting up to the specified wait time for
    // space to become available if the queue is full.
    public boolean offer(E e, long timeout, TimeUnit unit)
        throws InterruptedException
    {
        return linkedTransferQueue.offer(e, timeout, unit);
    }

    // Retrieves, but does not remove, the head of this
    // queue, or returns null if this queue is empty.
    public E peek() { return linkedTransferQueue.peek(); }

    // Retrieves and removes the head of this queue, or
    // returns null if this queue is empty.
    public E poll() { return linkedTransferQueue.poll(); }

    // Retrieves and removes the head of this queue, waiting
    // up to the specified wait time if necessary for an
    // element to become available.
    public E poll(long timeout, TimeUnit unit)
        throws InterruptedException
    {
        return linkedTransferQueue.poll(timeout, unit);
    }

    // Inserts the specified element at the tail of this
    // queue, waiting for space to become available if the
    // queue is full.
    public void put(E e) throws InterruptedException
    {
        linkedTransferQueue.put(e);
    }

    // Returns the number of additional elements that this
    // queue can ideally (in the absence of memory or
    // resource constraints) accept without blocking.
    public int remainingCapacity()
    {
        return linkedTransferQueue.remainingCapacity();
    }

    // Removes a single instance of the specified element
    // from this queue, if it is present.
    public boolean remove(Object o)
    {
        return linkedTransferQueue.remove(o);
    }

    // Returns the number of elements in this queue. **/
    public int size() { return linkedTransferQueue.size(); }

    // Retrieves and removes the head of this queue, waiting
    // if necessary until an element becomes available
    public E take() throws InterruptedException
    {
        return linkedTransferQueue.take();
    }

    // Returns an array containing all of the elements in
    // this queue, in proper sequence.
    public Object[] toArray()
    {
        return linkedTransferQueue.toArray();
    }

    // Returns an array containing all of the elements in
    // this queue, in proper sequence; the runtime type of
    //  the returned array is that of the specified array.
    public <T> T[] toArray(T[] a)
    {
        return linkedTransferQueue.toArray(a);
    }

    // Returns a string representation of this collection.
    public String toString()
    {
        return linkedTransferQueue.toString();
    }

    // Transfers the element to a consumer, waiting if
    // necessary to do so.
    public void transfer(E e) throws InterruptedException
    {
        linkedTransferQueue.transfer(e);
    }

    public static void main(String[] args)
    {
        // create a linkedtransfer queue
        LinkedTransferQueueImpl<String> linkedTransferQueue
            = new LinkedTransferQueueImpl<String>();

        try {

            // add elements
            linkedTransferQueue.put("1");
            linkedTransferQueue.put("2");
            linkedTransferQueue.put("3");
        }
        catch (InterruptedException e) {
            e.printStackTrace();
        }
        linkedTransferQueue.add("4");
        linkedTransferQueue.add("5");
        System.out.println(
            "the elements of the linkedTransferQueue is ");

        // iterate and print elements
        Iterator<String> itr
            = linkedTransferQueue.iterator();
        while (itr.hasNext()) {
            System.out.print(itr.next() + "\t");
        }
        System.out.println();
        linkedTransferQueue.offer("6");
        linkedTransferQueue.offer("7");
        System.out.println(
            "the peak element of the linkedTransferQueue is(by peeking) "
            + linkedTransferQueue.peek());
        System.out.println(
            "the peak element of the linkedTransferQueue is(by polling) "
            + linkedTransferQueue.poll());
        System.out.println(
            "the remaining capacity is "
            + linkedTransferQueue.remainingCapacity());
        System.out.println(
            "the remaining consumer waiting count : "
            + linkedTransferQueue
                  .getWaitingConsumerCount());
        System.out.println(
            "element 300 removed "
            + linkedTransferQueue.remove("3"));
        System.out.println(
            "the linkedTransferQueue contains 400 :"
            + linkedTransferQueue.contains("4"));
        System.out.println(
            "the linkedTransferQueue contains 100 :"
            + linkedTransferQueue.contains("1"));
        System.out.println(
            "the size of the linkedTransferQueue is "
            + linkedTransferQueue.size());
        System.out.println(linkedTransferQueue);
    }
}