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de.desy.acop.displayers.tools
Class DismissableBlockingQueue<E>

java.lang.Object
  java.util.AbstractCollection<E>
      java.util.AbstractQueue<E>
          de.desy.acop.displayers.tools.DismissableBlockingQueue<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 DismissableBlockingQueue<E>
extends java.util.AbstractQueue<E>
implements java.util.concurrent.BlockingQueue<E>, java.io.Serializable

Implementation of BlockingQueueu with fixed capacity. If maximum capacity is reached the last item in the queue is replaced with the newly added item.

Author:

Doug Lea, Jaka Bobnar, Cosylab

See Also:

Serialized Form

Constructor Summary

DismissableBlockingQueue(int capacity)
Creates an ArrayBlockingQueue with the given (fixed) capacity and default access policy.

DismissableBlockingQueue(int capacity, boolean fair)
Creates an ArrayBlockingQueue with the given (fixed) capacity and the specified access policy.

DismissableBlockingQueue(int capacity, boolean fair, java.util.Collection<? extends E> c)
Creates an ArrayBlockingQueue with the given (fixed) capacity, the specified access policy and initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Method Summary

boolean	add(E e) 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 throwing an IllegalStateException if this queue is full.
void	clear() Atomically removes all of the elements from this queue.
boolean	contains(java.lang.Object o) Returns true if this queue contains the specified element.
int	drainTo(java.util.Collection<? super E> c)
int	drainTo(java.util.Collection<? super E> c, int maxElements)
java.util.Iterator<E>	iterator() Returns an iterator over the elements in this queue in proper sequence.
boolean	offer(E e) 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.
boolean	offer(E e, long timeout, java.util.concurrent.TimeUnit unit) 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.
E	peek()
E	poll()
E	poll(long timeout, java.util.concurrent.TimeUnit unit)
void	put(E e) Inserts the specified element at the tail of this queue, waiting for space to become available if the queue is full.
int	remainingCapacity() Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking.
boolean	remove(java.lang.Object o) Removes a single instance of the specified element from this queue, if it is present.
int	size() Returns the number of elements in this queue.
E	take()
java.lang.Object[]	toArray() Returns an array containing all of the elements in this queue, in proper sequence.
<T> T[]	toArray(T[] a) 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.
java.lang.String	toString()

Methods inherited from class java.util.AbstractQueue

addAll, element, remove

Methods inherited from class java.util.AbstractCollection

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.Queue

element, remove

Methods inherited from interface java.util.Collection

addAll, containsAll, equals, hashCode, isEmpty, removeAll, retainAll

Constructor Detail

DismissableBlockingQueue

public DismissableBlockingQueue(int capacity)

Creates an ArrayBlockingQueue with the given (fixed) capacity and default access policy.

Parameters:

capacity - the capacity of this queue

Throws:

java.lang.IllegalArgumentException - if capacity is less than 1

DismissableBlockingQueue

public DismissableBlockingQueue(int capacity,
                                boolean fair)

Creates an ArrayBlockingQueue with the given (fixed) capacity and the specified access policy.

Parameters:

capacity - the capacity of this queue

fair - if true then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; if false the access order is unspecified.

Throws:

java.lang.IllegalArgumentException - if capacity is less than 1

DismissableBlockingQueue

public DismissableBlockingQueue(int capacity,
                                boolean fair,
                                java.util.Collection<? extends E> c)

Creates an ArrayBlockingQueue with the given (fixed) capacity, the specified access policy and initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Parameters:

capacity - the capacity of this queue

fair - if true then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; if false the access order is unspecified.

c - the collection of elements to initially contain

Throws:

java.lang.IllegalArgumentException - if capacity is less than c.size(), or less than 1.

java.lang.NullPointerException - if the specified collection or any of its elements are null

Method Detail

add

public boolean add(E e)

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 throwing an IllegalStateException if this queue is full.

Specified by:

add in interface java.util.Collection<E>

Specified by:

add in interface java.util.concurrent.BlockingQueue<E>

Specified by:

add in interface java.util.Queue<E>

Overrides:

add in class java.util.AbstractQueue<E>

Parameters:

e - the element to add

Returns:

true (as specified by Collection.add(E))

Throws:

java.lang.IllegalStateException - if this queue is full

java.lang.NullPointerException - if the specified element is null

offer

public boolean offer(E e)

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. This method is generally preferable to method add(E), which can fail to insert an element only by throwing an exception.

Specified by:

offer in interface java.util.concurrent.BlockingQueue<E>

Specified by:

offer in interface java.util.Queue<E>

Throws:

java.lang.NullPointerException - if the specified element is null

put

public void put(E e)
         throws java.lang.InterruptedException

Inserts the specified element at the tail of this queue, waiting for space to become available if the queue is full.

Specified by:

put in interface java.util.concurrent.BlockingQueue<E>

Throws:

java.lang.InterruptedException

java.lang.NullPointerException

offer

public boolean offer(E e,
                     long timeout,
                     java.util.concurrent.TimeUnit unit)
              throws java.lang.InterruptedException

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.

Specified by:

offer in interface java.util.concurrent.BlockingQueue<E>

Throws:

java.lang.InterruptedException

java.lang.NullPointerException

poll

public E poll()

Specified by:

poll in interface java.util.Queue<E>

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

peek

public E peek()

Specified by:

peek in interface java.util.Queue<E>

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

remainingCapacity

public int remainingCapacity()

Returns the number of additional 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 insert an element will succeed by inspecting remainingCapacity because it may be the case that another thread is about to insert or remove an element.

Specified by:

remainingCapacity in interface java.util.concurrent.BlockingQueue<E>

remove

public boolean remove(java.lang.Object o)

Removes a single instance of the specified element from this queue, if it is present. More formally, removes an element e such that o.equals(e), if this queue contains one or more such elements. Returns true if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).

Specified by:

remove in interface java.util.Collection<E>

Specified by:

remove in interface java.util.concurrent.BlockingQueue<E>

Overrides:

remove in class java.util.AbstractCollection<E>

Parameters:

o - element to be removed from this queue, if present

Returns:

true if this queue changed as a result of the call

contains

public boolean contains(java.lang.Object o)

Returns true if this queue contains the specified element. More formally, returns true if and only if this queue contains at least one element e such that o.equals(e).

Specified by:

contains in interface java.util.Collection<E>

Specified by:

contains in interface java.util.concurrent.BlockingQueue<E>

Overrides:

contains in class java.util.AbstractCollection<E>

Parameters:

o - object to be checked for containment in this queue

Returns:

true if this queue contains the specified element

toArray

public java.lang.Object[] toArray()

Returns an array containing all of the elements in this queue, in proper sequence.

The returned array will be "safe" in that no references to it are maintained by this queue. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Specified by:

toArray in interface java.util.Collection<E>

Overrides:

toArray in class java.util.AbstractCollection<E>

Returns:

an array containing all of the elements in this queue

toArray

public <T> T[] toArray(T[] a)

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. If the queue fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this queue.

If this queue fits in the specified array with room to spare (i.e., the array has more elements than this queue), the element in the array immediately following the end of the queue is set to null.

Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a queue known to contain only strings. The following code can be used to dump the queue into a newly allocated array of String:

     String[] y = x.toArray(new String[0]);

Note that toArray(new Object[0]) is identical in function to toArray().

Specified by:

toArray in interface java.util.Collection<E>

Overrides:

toArray in class java.util.AbstractCollection<E>

Parameters:

a - the array into which the elements of the queue are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose

Returns:

an array containing all of the elements in this queue

Throws:

java.lang.ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue

java.lang.NullPointerException - if the specified array is null

toString

public java.lang.String toString()

Overrides:

toString in class java.util.AbstractCollection<E>

clear

public void clear()

Atomically removes all of the elements from this queue. The queue will be empty after this call returns.

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>

Throws:

java.lang.UnsupportedOperationException

java.lang.ClassCastException

java.lang.NullPointerException

java.lang.IllegalArgumentException

drainTo

public int drainTo(java.util.Collection<? super E> c,
                   int maxElements)

Specified by:

drainTo in interface java.util.concurrent.BlockingQueue<E>

Throws:

java.lang.UnsupportedOperationException

java.lang.ClassCastException

java.lang.NullPointerException

java.lang.IllegalArgumentException

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.lang.Iterable<E>

Specified by:

iterator in interface java.util.Collection<E>

Specified by:

iterator in class java.util.AbstractCollection<E>

Returns:

an iterator over the elements in this queue in proper sequence