E - the type of elements held in this collectionpublic interface BlockingDeque<E> extends BlockingQueue<E>, Deque<E>
A Deque that additionally supports blocking operations that wait for the deque to become non-empty when retrieving an element, and wait for space to become available in the deque when storing an element.
BlockingDeque 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 null 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:
| First Element (Head) | ||||
| Throws exception | Special value | Blocks | Times out | |
| Insert | addFirst(e) | offerFirst(e) | putFirst(e) | offerFirst(e, time, unit) |
| Remove | removeFirst() | pollFirst() | takeFirst() | pollFirst(time, unit) |
| Examine | getFirst() | peekFirst() | not applicable | not applicable |
| Last Element (Tail) | ||||
| Throws exception | Special value | Blocks | Times out | |
| Insert | addLast(e) | offerLast(e) | putLast(e) | offerLast(e, time, unit) |
| Remove | removeLast() | pollLast() | takeLast() | pollLast(time, unit) |
| Examine | getLast() | peekLast() | not applicable | not applicable |
Like any BlockingQueue, a BlockingDeque is thread safe, does not permit null elements, and may (or may not) be capacity-constrained.
A BlockingDeque implementation may be used directly as a FIFO BlockingQueue. The methods inherited from the BlockingQueue interface are precisely equivalent to BlockingDeque methods as indicated in the following table:
BlockingQueue Method
| Equivalent BlockingDeque Method
|
| Insert | |
add(e) | addLast(e) |
offer(e) | offerLast(e) |
put(e) | putLast(e) |
offer(e, time, unit) | offerLast(e, time, unit) |
| Remove | |
remove() | removeFirst() |
poll() | pollFirst() |
take() | takeFirst() |
poll(time, unit) | pollFirst(time, unit) |
| Examine | |
element() | getFirst() |
peek() | peekFirst() |
Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a BlockingDeque happen-before actions subsequent to the access or removal of that element from the BlockingDeque in another thread.
This interface is a member of the Java Collections Framework.
void addFirst(E e)
Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerFirst.
addFirst in interface Deque<E>
e - the element to addIllegalStateException - if the element cannot be added at this time due to capacity restrictionsClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequevoid addLast(E e)
Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offerLast.
addLast in interface Deque<E>
e - the element to addIllegalStateException - if the element cannot be added at this time due to capacity restrictionsClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offerFirst(E e)
Inserts the specified element at the front of this deque if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addFirst method, which can fail to insert an element only by throwing an exception.
offerFirst in interface Deque<E>
e - the element to addtrue if the element was added to this deque, else false
ClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offerLast(E e)
Inserts the specified element at the end of this deque if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the addLast method, which can fail to insert an element only by throwing an exception.
offerLast in interface Deque<E>
e - the element to addtrue if the element was added to this deque, else false
ClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequevoid putFirst(E e)
throws InterruptedException Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
e - the element to addInterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequevoid putLast(E e)
throws InterruptedException Inserts the specified element at the end of this deque, waiting if necessary for space to become available.
e - the element to addInterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offerFirst(E e,
long timeout,
TimeUnit unit)
throws InterruptedException Inserts the specified element at the front of this deque, waiting up to the specified wait time if necessary for space to become available.
e - the element to addtimeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parametertrue if successful, or false if the specified waiting time elapses before space is availableInterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offerLast(E e,
long timeout,
TimeUnit unit)
throws InterruptedException Inserts the specified element at the end of this deque, waiting up to the specified wait time if necessary for space to become available.
e - the element to addtimeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parametertrue if successful, or false if the specified waiting time elapses before space is availableInterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeE takeFirst()
throws InterruptedException Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
InterruptedException - if interrupted while waitingE takeLast()
throws InterruptedException Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.
InterruptedException - if interrupted while waitingE pollFirst(long timeout,
TimeUnit unit)
throws InterruptedException Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available.
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameternull if the specified waiting time elapses before an element is availableInterruptedException - if interrupted while waitingE pollLast(long timeout,
TimeUnit unit)
throws InterruptedException Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available.
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameternull if the specified waiting time elapses before an element is availableInterruptedException - if interrupted while waitingboolean removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
removeFirstOccurrence in interface Deque<E>
o - element to be removed from this deque, if presenttrue if an element was removed as a result of this callClassCastException - if the class of the specified element is incompatible with this deque (optional)NullPointerException - if the specified element is null (optional)boolean removeLastOccurrence(Object o)
Removes the last occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the last element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
removeLastOccurrence in interface Deque<E>
o - element to be removed from this deque, if presenttrue if an element was removed as a result of this callClassCastException - if the class of the specified element is incompatible with this deque (optional)NullPointerException - if the specified element is null (optional)boolean add(E e)
Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available. When using a capacity-restricted deque, it is generally preferable to use offer.
This method is equivalent to addLast.
add in interface BlockingQueue<E>
add in interface Collection<E>
add in interface Deque<E>
add in interface Queue<E>
e - the element to addtrue (as specified by Collection.add(E))IllegalStateException - if the element cannot be added at this time due to capacity restrictionsClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offer(E e)
Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) if it is possible to do so immediately without violating capacity restrictions, returning true upon success and false if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the add(E) method, which can fail to insert an element only by throwing an exception.
This method is equivalent to offerLast.
offer in interface BlockingQueue<E>
offer in interface Deque<E>
offer in interface Queue<E>
e - the element to addtrue if the element was added to this queue, else false
ClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequevoid put(E e) throws InterruptedException
Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available.
This method is equivalent to putLast.
put in interface BlockingQueue<E>
e - the element to addInterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeboolean offer(E e,
long timeout,
TimeUnit unit)
throws InterruptedException Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available.
This method is equivalent to offerLast.
offer in interface BlockingQueue<E>
e - the element to addtimeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parametertrue if the element was added to this deque, else false
InterruptedException - if interrupted while waitingClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this dequeE remove()
Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque). This method differs from poll only in that it throws an exception if this deque is empty.
This method is equivalent to removeFirst.
remove in interface Deque<E>
remove in interface Queue<E>
NoSuchElementException - if this deque is emptyE poll()
Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.
This method is equivalent to Deque.pollFirst().
poll in interface Deque<E>
poll in interface Queue<E>
null if this deque is emptyE take() throws InterruptedException
Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available.
This method is equivalent to takeFirst.
take in interface BlockingQueue<E>
InterruptedException - if interrupted while waitingE poll(long timeout,
TimeUnit unit)
throws InterruptedException Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available.
This method is equivalent to pollFirst.
poll in interface BlockingQueue<E>
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameternull if the specified waiting time elapses before an element is availableInterruptedException - if interrupted while waitingE element()
Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque). This method differs from peek only in that it throws an exception if this deque is empty.
This method is equivalent to getFirst.
element in interface Deque<E>
element in interface Queue<E>
NoSuchElementException - if this deque is emptyE peek()
Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.
This method is equivalent to peekFirst.
peek in interface Deque<E>
peek in interface Queue<E>
null if this deque is emptyboolean remove(Object o)
Removes the first occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).
This method is equivalent to removeFirstOccurrence.
remove in interface BlockingQueue<E>
remove in interface Collection<E>
remove in interface Deque<E>
o - element to be removed from this deque, if presenttrue if this deque changed as a result of the callClassCastException - if the class of the specified element is incompatible with this deque (optional)NullPointerException - if the specified element is null (optional)boolean contains(Object o)
Returns true if this deque contains the specified element. More formally, returns true if and only if this deque contains at least one element e such that o.equals(e).
contains in interface BlockingQueue<E>
contains in interface Collection<E>
contains in interface Deque<E>
o - object to be checked for containment in this dequetrue if this deque contains the specified elementClassCastException - if the class of the specified element is incompatible with this deque (optional)NullPointerException - if the specified element is null (optional)int size()
Returns the number of elements in this deque.
size in interface Collection<E>
size in interface Deque<E>
Iterator<E> iterator()
Returns an iterator over the elements in this deque in proper sequence. The elements will be returned in order from first (head) to last (tail).
iterator in interface Collection<E>
iterator in interface Deque<E>
iterator in interface Iterable<E>
void push(E e)
Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available.
This method is equivalent to addFirst.
push in interface Deque<E>
e - the element to pushIllegalStateException - if the element cannot be added at this time due to capacity restrictionsClassCastException - if the class of the specified element prevents it from being added to this dequeNullPointerException - if the specified element is nullIllegalArgumentException - if some property of the specified element prevents it from being added to this deque
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