Class VariableLinkedBlockingQueue<E>

  • Type Parameters:
    E - the type of elements held in this collection
    All Implemented Interfaces:
    Serializable, Iterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>

    public class VariableLinkedBlockingQueue<E>
    extends AbstractQueue<E>
    implements BlockingQueue<E>, Serializable
    A clone of LinkedBlockingQueue with the addition of a setCapacity(int) method, allowing us to change the capacity of the queue while it is in use.

    The documentation for LinkedBlockingQueue follows...

    An optionally-bounded blocking queue based on linked nodes. This queue orders elements FIFO (first-in-first-out). The head of the queue is that element that has been on the queue the longest time. The tail of the queue is that element that has been on the queue the shortest time. New elements are inserted at the tail of the queue, and the queue retrieval operations obtain elements at the head of the queue. Linked queues typically have higher throughput than array-based queues but less predictable performance in most concurrent applications.

    The optional capacity bound constructor argument serves as a way to prevent excessive queue expansion. The capacity, if unspecified, is equal to Integer.MAX_VALUE. Linked nodes are dynamically created upon each insertion unless this would bring the queue above capacity.

    This class implements all of the optional methods of the Collection and Iterator interfaces.

    This class is a member of the Java Collections Framework.

    Doug Lea
    See Also:
    Serialized Form
    • Constructor Detail

      • VariableLinkedBlockingQueue

        public VariableLinkedBlockingQueue()
        Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE.
      • VariableLinkedBlockingQueue

        public VariableLinkedBlockingQueue​(int capacity)
        Creates a LinkedBlockingQueue with the given (fixed) capacity.
        capacity - the capacity of this queue.
        IllegalArgumentException - if capacity is not greater than zero.
      • VariableLinkedBlockingQueue

        public VariableLinkedBlockingQueue​(Collection<? extends E> c)
        Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE, initially containing the elements of the given collection, added in traversal order of the collection's iterator.
        c - the collection of elements to initially contain
        NullPointerException - if c or any element within it is null
    • Method Detail

      • size

        public int size()
        Returns the number of elements in this queue.
        Specified by:
        size in interface Collection<E>
        Specified by:
        size in class AbstractCollection<E>
        the number of elements in this queue.
      • setCapacity

        public void setCapacity​(int capacity)
        Set a new capacity for the queue. Increasing the capacity can cause any waiting put(Object) invocations to succeed if the new capacity is larger than the queue.
        capacity - the new capacity for the queue
      • remainingCapacity

        public int remainingCapacity()
        Returns the number of elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking. This is always equal to the initial capacity of this queue less the current size of this queue.

        Note that you cannot always tell if an attempt to add an element will succeed by inspecting remainingCapacity because it may be the case that a waiting consumer is ready to take an element out of an otherwise full queue.

        Specified by:
        remainingCapacity in interface BlockingQueue<E>
      • offer

        public boolean offer​(E o,
                             long timeout,
                             TimeUnit unit)
                      throws InterruptedException
        Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available.
        Specified by:
        offer in interface BlockingQueue<E>
        o - the element to add
        timeout - how long to wait before giving up, in units of unit
        unit - a TimeUnit determining how to interpret the timeout parameter
        true if successful, or false if the specified waiting time elapses before space is available.
        InterruptedException - if interrupted while waiting.
        NullPointerException - if the specified element is null.
      • offer

        public boolean offer​(E o)
        Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full.
        Specified by:
        offer in interface BlockingQueue<E>
        Specified by:
        offer in interface Queue<E>
        o - the element to add.
        true if it was possible to add the element to this queue, else false
        NullPointerException - if the specified element is null
      • poll

        public E poll()
        Specified by:
        poll in interface Queue<E>
      • peek

        public E peek()
        Specified by:
        peek in interface Queue<E>
      • iterator

        public Iterator<E> iterator()
        Returns an iterator over the elements in this queue in proper sequence. The returned Iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.
        Specified by:
        iterator in interface Collection<E>
        Specified by:
        iterator in interface Iterable<E>
        Specified by:
        iterator in class AbstractCollection<E>
        an iterator over the elements in this queue in proper sequence.