Package com.rabbitmq.client.impl

Class VariableLinkedBlockingQueue<E>

  • Type Parameters:
    E - the type of elements held in this collection
    All Implemented Interfaces:
    java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, java.util.concurrent.BlockingQueue<E>, java.util.Queue<E>
    public class VariableLinkedBlockingQueue<E>
extends java.util.AbstractQueue<E>
implements java.util.concurrent.BlockingQueue<E>, java.io.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.

    Since:
    1.5
    See Also:
    Serialized Form

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private int capacity
      The capacity bound, or Integer.MAX_VALUE if none
      private java.util.concurrent.atomic.AtomicInteger count
      Current number of elements
      private VariableLinkedBlockingQueue.Node<E> head
      Head of linked list
      private VariableLinkedBlockingQueue.Node<E> last
      Tail of linked list
      private java.util.concurrent.locks.Condition notEmpty
      Wait queue for waiting takes
      private java.util.concurrent.locks.Condition notFull
      Wait queue for waiting puts
      private java.util.concurrent.locks.ReentrantLock putLock
      Lock held by put, offer, etc
      private static long serialVersionUID  
      private java.util.concurrent.locks.ReentrantLock takeLock
      Lock held by take, poll, etc

    • Constructor Summary

      Constructors 
      Constructor Description
      VariableLinkedBlockingQueue()
      Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE.
      VariableLinkedBlockingQueue​(int capacity)
      Creates a LinkedBlockingQueue with the given (fixed) capacity.
      VariableLinkedBlockingQueue​(java.util.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.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()  
      int drainTo​(java.util.Collection<? super E> c)  
      int drainTo​(java.util.Collection<? super E> c, int maxElements)  
      private E extract()
      Remove a node from head of queue,
      private void fullyLock()
      Lock to prevent both puts and takes.
      private void fullyUnlock()
      Unlock to allow both puts and takes.
      private void insert​(E x)
      Create a node and link it at end of queue
      java.util.Iterator<E> iterator()
      Returns an iterator over the elements in this queue in proper sequence.
      boolean offer​(E o)
      Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full.
      boolean offer​(E o, long timeout, java.util.concurrent.TimeUnit unit)
      Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available.
      E peek()  
      E poll()  
      E poll​(long timeout, java.util.concurrent.TimeUnit unit)  
      void put​(E o)
      Adds the specified element to the tail of this queue, waiting if necessary for space to become available.
      private void readObject​(java.io.ObjectInputStream s)
      Reconstitute this queue instance from a stream (that is, deserialize it).
      int remainingCapacity()
      Returns the number of elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking.
      boolean remove​(java.lang.Object o)  
      void setCapacity​(int capacity)
      Set a new capacity for the queue.
      private void signalNotEmpty()
      Signal a waiting take.
      private void signalNotFull()
      Signal a waiting put.
      int size()
      Returns the number of elements in this queue.
      E take()  
      java.lang.Object[] toArray()  
      <T> T[] toArray​(T[] a)  
      java.lang.String toString()  
      private void writeObject​(java.io.ObjectOutputStream s)
      Save the state to a stream (that is, serialize it).

      • Methods inherited from class java.util.AbstractQueue

        add, addAll, element, remove

      • Methods inherited from class java.util.AbstractCollection

        contains, containsAll, isEmpty, removeAll, retainAll

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.concurrent.BlockingQueue

        add, contains

      • Methods inherited from interface java.util.Collection

        addAll, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray

      • Methods inherited from interface java.lang.Iterable

        forEach

      • Methods inherited from interface java.util.Queue

        element, remove

    • Field Detail

      • capacity

        private int capacity
        The capacity bound, or Integer.MAX_VALUE if none

      • count

        private final java.util.concurrent.atomic.AtomicInteger count
        Current number of elements

      • takeLock

        private final java.util.concurrent.locks.ReentrantLock takeLock
        Lock held by take, poll, etc

      • notEmpty

        private final java.util.concurrent.locks.Condition notEmpty
        Wait queue for waiting takes

      • putLock

        private final java.util.concurrent.locks.ReentrantLock putLock
        Lock held by put, offer, etc

      • notFull

        private final java.util.concurrent.locks.Condition notFull
        Wait queue for waiting puts

    • 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.
        Parameters:
        capacity - the capacity of this queue.
        Throws:
        java.lang.IllegalArgumentException - if capacity is not greater than zero.

      • VariableLinkedBlockingQueue

        public VariableLinkedBlockingQueue​(java.util.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.
        Parameters:
        c - the collection of elements to initially contain
        Throws:
        java.lang.NullPointerException - if c or any element within it is null

    • Method Detail

      • signalNotEmpty

        private void signalNotEmpty()
        Signal a waiting take. Called only from put/offer (which do not otherwise ordinarily lock takeLock.)

      • signalNotFull

        private void signalNotFull()
        Signal a waiting put. Called only from take/poll.

      • insert

        private void insert​(E x)
        Create a node and link it at end of queue
        Parameters:
        x - the item

      • extract

        private E extract()
        Remove a node from head of queue,
        Returns:
        the node

      • fullyLock

        private void fullyLock()
        Lock to prevent both puts and takes.

      • fullyUnlock

        private void fullyUnlock()
        Unlock to allow both puts and takes.

      • size

        public int size()
        Returns the number of elements in this queue.
        Specified by:
        size in interface java.util.Collection<E>
        Specified by:
        size in class java.util.AbstractCollection<E>
        Returns:
        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.
        Parameters:
        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 java.util.concurrent.BlockingQueue<E>

      • put

        public void put​(E o)
         throws java.lang.InterruptedException
        Adds the specified element to the tail of this queue, waiting if necessary for space to become available.
        Specified by:
        put in interface java.util.concurrent.BlockingQueue<E>
        Parameters:
        o - the element to add
        Throws:
        java.lang.InterruptedException - if interrupted while waiting.
        java.lang.NullPointerException - if the specified element is null.

      • offer

        public boolean offer​(E o,
                     long timeout,
                     java.util.concurrent.TimeUnit unit)
              throws java.lang.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 java.util.concurrent.BlockingQueue<E>
        Parameters:
        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
        Returns:
        true if successful, or false if the specified waiting time elapses before space is available.
        Throws:
        java.lang.InterruptedException - if interrupted while waiting.
        java.lang.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 java.util.concurrent.BlockingQueue<E>
        Specified by:
        offer in interface java.util.Queue<E>
        Parameters:
        o - the element to add.
        Returns:
        true if it was possible to add the element to this queue, else false
        Throws:
        java.lang.NullPointerException - if the specified element is null

      • take

        public E take()
       throws java.lang.InterruptedException
        Specified by:
        take in interface java.util.concurrent.BlockingQueue<E>
        Throws:
        java.lang.InterruptedException

      • poll

        public E poll​(long timeout,
              java.util.concurrent.TimeUnit unit)
       throws java.lang.InterruptedException
        Specified by:
        poll in interface java.util.concurrent.BlockingQueue<E>
        Throws:
        java.lang.InterruptedException

      • poll

        public E poll()
        Specified by:
        poll in interface java.util.Queue<E>

      • peek

        public E peek()
        Specified by:
        peek in interface java.util.Queue<E>

      • remove

        public boolean remove​(java.lang.Object o)
        Specified by:
        remove in interface java.util.concurrent.BlockingQueue<E>
        Specified by:
        remove in interface java.util.Collection<E>
        Overrides:
        remove in class java.util.AbstractCollection<E>

      • toArray

        public java.lang.Object[] toArray()
        Specified by:
        toArray in interface java.util.Collection<E>
        Overrides:
        toArray in class java.util.AbstractCollection<E>

      • toArray

        public <T> T[] toArray​(T[] a)
        Specified by:
        toArray in interface java.util.Collection<E>
        Overrides:
        toArray in class java.util.AbstractCollection<E>

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.util.AbstractCollection<E>

      • clear

        public void clear()
        Specified by:
        clear in interface java.util.Collection<E>
        Overrides:
        clear in class java.util.AbstractQueue<E>

      • drainTo

        public int drainTo​(java.util.Collection<? super E> c)
        Specified by:
        drainTo in interface java.util.concurrent.BlockingQueue<E>

      • drainTo

        public int drainTo​(java.util.Collection<? super E> c,
                   int maxElements)
        Specified by:
        drainTo in interface java.util.concurrent.BlockingQueue<E>

      • iterator

        public java.util.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 java.util.Collection<E>
        Specified by:
        iterator in interface java.lang.Iterable<E>
        Specified by:
        iterator in class java.util.AbstractCollection<E>
        Returns:
        an iterator over the elements in this queue in proper sequence.

      • writeObject

        private void writeObject​(java.io.ObjectOutputStream s)
                  throws java.io.IOException
        Save the state to a stream (that is, serialize it).
        Parameters:
        s - the stream
        Throws:
        java.io.IOException

      • readObject

        private void readObject​(java.io.ObjectInputStream s)
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException
        Reconstitute this queue instance from a stream (that is, deserialize it).
        Parameters:
        s - the stream
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException