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public interface BlockingDeque
extends BlockingQueue, Deque
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 |
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() |
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
../../../../../../../../guide/collections/index.html">
Java Collections Framework.
Method Summary | |
boolean |
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void |
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void |
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boolean |
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Object |
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Iterator |
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boolean |
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boolean |
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boolean |
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boolean |
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boolean | |
Object |
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Object |
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Object | |
Object | |
Object | |
void |
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void |
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void |
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void |
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Object |
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boolean |
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boolean |
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boolean |
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int |
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Object |
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Object |
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Methods inherited from interface edu.emory.mathcs.backport.java.util.concurrent.BlockingQueue | |
add , contains , drainTo , drainTo , offer , offer , poll , put , remainingCapacity , remove , take |
Methods inherited from interface edu.emory.mathcs.backport.java.util.Deque | |
add , addFirst , addLast , contains , descendingIterator , element , getFirst , getLast , iterator , offer , offerFirst , offerLast , peek , peekFirst , peekLast , poll , pollFirst , pollLast , pop , push , remove , remove , removeFirst , removeFirstOccurrence , removeLast , removeLastOccurrence , size |
Methods inherited from interface edu.emory.mathcs.backport.java.util.Queue | |
add , element , offer , peek , poll , remove |
public boolean add(Object 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 useoffer
. This method is equivalent toaddLast
.
- Parameters:
e
- the element to add
public void addFirst(Object 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 useofferFirst
.
- Parameters:
e
- the element to add
public void addLast(Object 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 useofferLast
.
- Parameters:
e
- the element to add
public 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).
- Specified by:
- contains in interface BlockingQueue
- contains in interface Deque
- Parameters:
o
- object to be checked for containment in this deque
- Returns:
- true if this deque contains the specified element
public Object 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 frompeek
only in that it throws an exception if this deque is empty. This method is equivalent togetFirst
.
- Returns:
- the head of this deque
public Iterator 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).
- Returns:
- an iterator over the elements in this deque in proper sequence
public boolean offer(Object 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 theadd(Object)
method, which can fail to insert an element only by throwing an exception. This method is equivalent toofferLast
.
- Parameters:
e
- the element to add
public boolean offer(Object 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 toofferLast
.
- Specified by:
- offer in interface BlockingQueue
- Parameters:
e
- the element to add
- Returns:
- true if the element was added to this deque, else false
public boolean offerFirst(Object 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 theaddFirst
method, which can fail to insert an element only by throwing an exception.
- Specified by:
- offerFirst in interface Deque
- Parameters:
e
- the element to add
public boolean offerFirst(Object 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.
- Parameters:
e
- the element to addtimeout
- how long to wait before giving up, in units of unitunit
- 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
public boolean offerLast(Object 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 theaddLast
method, which can fail to insert an element only by throwing an exception.
- Parameters:
e
- the element to add
public boolean offerLast(Object 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.
- Parameters:
e
- the element to addtimeout
- how long to wait before giving up, in units of unitunit
- 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
public Object 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 topeekFirst
.
- Returns:
- the head of this deque, or null if this deque is empty
public Object 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 topollFirst()
.
- Returns:
- the head of this deque, or null if this deque is empty
public Object 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 topollFirst
.
- Specified by:
- poll in interface BlockingQueue
- Returns:
- the head of this deque, or null if the specified waiting time elapses before an element is available
public Object 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.
- Parameters:
timeout
- how long to wait before giving up, in units of unitunit
- a TimeUnit determining how to interpret the timeout parameter
- Returns:
- the head of this deque, or null if the specified waiting time elapses before an element is available
public Object 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.
- Parameters:
timeout
- how long to wait before giving up, in units of unitunit
- a TimeUnit determining how to interpret the timeout parameter
- Returns:
- the tail of this deque, or null if the specified waiting time elapses before an element is available
public void push(Object e)
Pushes an element onto the stack represented by this deque. In other words, inserts the element at the front of this deque unless it would violate capacity restrictions. This method is equivalent toaddFirst
.
public void put(Object 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 toputLast
.
- Specified by:
- put in interface BlockingQueue
- Parameters:
e
- the element to add
public void putFirst(Object e) throws InterruptedException
Inserts the specified element at the front of this deque, waiting if necessary for space to become available.
- Parameters:
e
- the element to add
public void putLast(Object e) throws InterruptedException
Inserts the specified element at the end of this deque, waiting if necessary for space to become available.
- Parameters:
e
- the element to add
public Object 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 frompoll
only in that it throws an exception if this deque is empty. This method is equivalent toremoveFirst
.
- Returns:
- the head of the queue represented by this deque
public boolean 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 toremoveFirstOccurrence
.
- Specified by:
- remove in interface BlockingQueue
- remove in interface Deque
- Parameters:
o
- element to be removed from this deque, if present
- Returns:
- true if this deque changed as a result of the call
public boolean 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).
- Specified by:
- removeFirstOccurrence in interface Deque
- Parameters:
o
- element to be removed from this deque, if present
- Returns:
- true if an element was removed as a result of this call
public 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).
- Specified by:
- removeLastOccurrence in interface Deque
- Parameters:
o
- element to be removed from this deque, if present
- Returns:
- true if an element was removed as a result of this call
public int size()
Returns the number of elements in this deque.
- Returns:
- the number of elements in this deque
public Object 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 totakeFirst
.
- Specified by:
- take in interface BlockingQueue
- Returns:
- the head of this deque
public Object takeFirst() throws InterruptedException
Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available.
- Returns:
- the head of this deque
public Object takeLast() throws InterruptedException
Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available.
- Returns:
- the tail of this deque