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virtual | ~BlockingQueue () |
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virtual void | put (const E &value)=0 |
| Inserts the specified element into this queue, waiting if necessary for space to become available. More...
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virtual bool | offer (const E &e, long long timeout, const TimeUnit &unit)=0 |
| Inserts the specified element into this queue, waiting up to the specified wait time if necessary for space to become available. More...
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virtual E | take ()=0 |
| Retrieves and removes the head of this queue, waiting if necessary until an element becomes available. More...
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virtual bool | poll (E &result, long long timeout, const TimeUnit &unit)=0 |
| Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available. More...
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virtual int | remainingCapacity () const =0 |
| Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or Integer::MAX_VALUE if there is no intrinsic limit. More...
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virtual int | drainTo (Collection< E > &c)=0 |
| Removes all available elements from this queue and adds them to the given collection. More...
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virtual int | drainTo (Collection< E > &c, int maxElements)=0 |
| Removes at most the given number of available elements from this queue and adds them to the given collection. More...
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| AbstractQueue () |
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virtual | ~AbstractQueue () |
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virtual bool | add (const E &value) |
| Returns true if this collection changed as a result of the call.(Returns false if this collection does not permit duplicates and already contains the specified element.)Collections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added.If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning false). This preserves the invariant that a collection always contains the specified element after this call returns.For non-pointer values, i.e. class instances or string's the object will be copied into the collection, thus the object must support being copied, must not hide the copy constructor and assignment operator.- Parameters
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value | The reference to the element to add to this Collection. |
- Returns
- true if the element was added to this Collection.
- Exceptions
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UnsupportedOperationExceptio | if this is an unmodifiable collection. |
NullPointerException | if the Collection is a container of pointers and does not allow NULL values. |
IllegalArgumentException | if some property of the element prevents it from being added to this collection |
IllegalStateException | if the element cannot be added at this time due to insertion restrictions. |
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virtual bool | addAll (const Collection< E > &collection) |
| Adds all of the elements in the specified collection to this collection.The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this collection, and this collection is nonempty.)- Parameters
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collection | The Collection whose elements are added to this one. |
- Returns
- true if this collection changed as a result of the call
- Exceptions
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UnsupportedOperationExceptio | if this is an unmodifiable collection. |
NullPointerException | if the Collection is a container of pointers and does not allow NULL values. |
IllegalArgumentException | if some property of an element prevents it from being added to this collection |
IllegalStateException | if an element cannot be added at this time due to insertion restrictions. |
This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.Note that this implementation will throw an UnsupportedOperationException unless add is overridden (assuming the specified collection is non-empty). More...
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virtual E | remove () |
| Gets and removes the element in the head of the queue.Throws a NoSuchElementException if there is no element in the queue.- Returns
- the element in the head of the queue.
- Exceptions
-
More...
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virtual E | element () const |
| Gets but not removes the element in the head of the queue.Throws a NoSuchElementException if there is no element in the queue.- Returns
- the element in the head of the queue.
- Exceptions
-
More...
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virtual void | clear () |
| Removes all of the elements from this collection (optional operation).The collection will be empty after this method returns.This implementation iterates over this collection, removing each element using the Iterator.remove operation. Most implementations will probably choose to override this method for efficiency.Note that this implementation will throw an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection is non-empty.- Exceptions
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UnsupportedOperationException | if the clear operation is not supported by this collection |
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virtual | ~Queue () |
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virtual bool | offer (const E &value)=0 |
| Inserts the specified element into the queue provided that the condition allows such an operation. More...
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virtual bool | poll (E &result)=0 |
| Gets and removes the element in the head of the queue. More...
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virtual bool | peek (E &result) const =0 |
| Gets but not removes the element in the head of the queue. More...
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virtual | ~Collection () |
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virtual int | size () const =0 |
| Returns the number of elements in this collection. More...
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virtual | ~Iterable () |
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virtual decaf::util::Iterator
< E > * | iterator ()=0 |
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virtual decaf::util::Iterator
< E > * | iterator () const =0 |
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virtual | ~Synchronizable () |
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| AbstractCollection () |
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| AbstractCollection (const AbstractCollection &other) |
| Copy Constructor, copy element from the source collection to this collection after clearing any element stored in this collection. More...
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virtual | ~AbstractCollection () |
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AbstractCollection< E > & | operator= (const AbstractCollection< E > &collection) |
| Assignment Operator, copy element from the source collection to this collection after clearing any element stored in this collection. More...
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virtual bool | contains (const E &value) const |
| Returns true if this collection contains the specified element.More formally, returns true if and only if this collection contains at least one element e such that (value == NULL ? e == NULL : value == e ).- Parameters
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value | The value to check for presence in the collection. |
- Returns
- true if there is at least one of the elements in the collection
- Exceptions
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NullPointerException | if the Collection contains pointers and the Collection does not allow for NULL elements (optional check). |
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virtual bool | containsAll (const Collection< E > &collection) const |
| Returns true if this collection contains all of the elements in the specified collection.- Parameters
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- Exceptions
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NullPointerException | if the Collection contains pointers and the Collection does not allow for NULL elements (optional check). |
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virtual bool | equals (const Collection< E > &collection) const |
| Answers true if this Collection and the one given are the same size and if each element contained in the Collection given is equal to an element contained in this collection. More...
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virtual void | copy (const Collection< E > &collection) |
| Renders this Collection as a Copy of the given Collection. More...
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virtual bool | isEmpty () const |
| Returns true if this collection contains no elements. More...
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virtual bool | add (const E &value DECAF_UNUSED) |
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virtual bool | remove (const E &value) |
| Removes a single instance of the specified element from the collection.More formally, removes an element e such that (value == NULL ? e == NULL : value == e), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).- Parameters
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value | The reference to the element to remove from this Collection. |
- Returns
- true if the collection was changed, false otherwise.
- Exceptions
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UnsupportedOperationExceptio | if this is an unmodifiable collection. |
NullPointerException | if the Collection is a container of pointers and does not allow NULL values. |
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virtual bool | removeAll (const Collection< E > &collection) |
| Removes all this collection's elements that are also contained in the specified collection (optional operation).After this call returns, this collection will contain no elements in common with the specified collection.- Parameters
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collection | The Collection whose elements are to be removed from this one. |
- Returns
- true if the collection changed as a result of this call.
- Exceptions
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UnsupportedOperationExceptio | if this is an unmodifiable collection. |
NullPointerException | if the Collection is a container of pointers and does not allow NULL values. |
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virtual bool | retainAll (const Collection< E > &collection) |
| Retains only the elements in this collection that are contained in the specified collection (optional operation).In other words, removes from this collection all of its elements that are not contained in the specified collection.- Parameters
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collection | The Collection whose elements are to be retained. |
- Returns
- true if the collection changed as a result of this call.
- Exceptions
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UnsupportedOperationExceptio | if this is an unmodifiable collection. |
NullPointerException | if the Collection is a container of pointers and does not allow NULL values. |
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virtual std::vector< E > | toArray () const |
| Answers an STL vector containing copies of all elements contained in this Collection. More...
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virtual void | lock () |
| Locks the object. More...
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virtual bool | tryLock () |
| Attempts to Lock the object, if the lock is already held by another thread than this method returns false. More...
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virtual void | unlock () |
| Unlocks the object. More...
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virtual void | wait () |
| Waits on a signal from this object, which is generated by a call to Notify. More...
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virtual void | wait (long long millisecs) |
| Waits on a signal from this object, which is generated by a call to Notify. More...
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virtual void | wait (long long millisecs, int nanos) |
| Waits on a signal from this object, which is generated by a call to Notify. More...
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virtual void | notify () |
| Signals a waiter on this object that it can now wake up and continue. More...
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virtual void | notifyAll () |
| Signals the waiters on this object that it can now wake up and continue. More...
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template<typename E>
class decaf::util::concurrent::BlockingQueue< E >
A decaf::util::Queue that additionally supports operations that wait for the queue to become non-empty when retrieving an element, and wait for space to become available in the queue when storing an element.
BlockingQueue
methods come in four forms, with different ways of handling operations that cannot be satisfied immediately, but may be satisfied at some point in the future: one throws an exception, the second returns a special value (either true
or false
, depending on the operation), the third blocks the current thread indefinitely until the operation can succeed, and the fourth blocks for only a given maximum time limit before giving up. These methods are summarized in the following table:
A BlockingQueue
may be capacity bounded. At any given time it may have a remainingCapacity
beyond which no additional elements can be put
without blocking. A BlockingQueue
without any intrinsic capacity constraints always reports a remaining capacity of Integer::MAX_VALUE
.
BlockingQueue
implementations are designed to be used primarily for producer-consumer queues, but additionally support decaf::util::Collection interface. So, for example, it is possible to remove an arbitrary element from a queue using remove(x)
. However, such operations are in general not performed very efficiently, and are intended for only occasional use, such as when a queued message is cancelled.
BlockingQueue
implementations are thread-safe. All queuing methods achieve their effects atomically using internal locks or other forms of concurrency control. However, the bulk Collection operations addAll
, containsAll
, retainAll
and removeAll
are not necessarily performed atomically unless specified otherwise in an implementation. So it is possible, for example, for addAll(c)
to fail (throwing an exception) after adding only some of the elements in c
.
A BlockingQueue
does not intrinsically support any kind of "close" or "shutdown" operation to indicate that no more items will be added. The needs and usage of such features tend to be implementation-dependent. For example, a common tactic is for producers to insert special end-of-stream or poison objects, that are interpreted accordingly when taken by consumers.
Usage example, based on a typical producer-consumer scenario. Note that a BlockingQueue
can safely be used with multiple producers and multiple consumers.
class Producer : public Runnable {
private:
BlockingQueue* queue;
public:
Producer( BlockingQueue* q ) : queue( q ) {}
virtual void run() {
try {
while( true ) { queue->put( produce() ); }
} catch( InterruptedException& ex ) { ... handle ...}
}
Object produce() { ... }
}
class Consumer : public Runnable {
private:
BlockingQueue* queue;
public:
Consumer( BlockingQueue* q ) : queue( q ) {}
virtual void run() {
try {
while( true ) { consume( queue->take() ); }
} catch( InterruptedException& ex ) { ... handle ...}
}
void consume( Object& x ) { ... }
}
int main( int argc, char** argv ) {
BlockingQueue q = new SomeQueueImplementation();
Producer p( &q );
Consumer c1( &q );
Consumer c2( &q );
Thread t1( &p ).start();
Thread t2( &c1 ).start();
Thread t3( &c2 ).start();
}
Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a BlockingQueue happen-before actions subsequent to the access or removal of that element from the BlockingQueue in another thread.
- Since
- 1.0