PriorityBlockingQueue (Java Platform SE 6) (original) (raw)

java.util.concurrent

Class PriorityBlockingQueue

java.lang.Object extended by java.util.AbstractCollection java.util.AbstractQueue java.util.concurrent.PriorityBlockingQueue

Type Parameters:

E - the type of elements held in this collection

All Implemented Interfaces:

Serializable, Iterable, Collection, BlockingQueue, Queue

public class PriorityBlockingQueue

extends AbstractQueue

implements BlockingQueue, Serializable

An unbounded blocking queue that uses the same ordering rules as class PriorityQueue and supplies blocking retrieval operations. While this queue is logically unbounded, attempted additions may fail due to resource exhaustion (causing OutOfMemoryError). This class does not permitnull elements. A priority queue relying on natural ordering also does not permit insertion of non-comparable objects (doing so results inClassCastException).

This class and its iterator implement all of the_optional_ methods of the Collection and Iterator interfaces. The Iterator provided in method iterator() is not guaranteed to traverse the elements of the PriorityBlockingQueue in any particular order. If you need ordered traversal, consider usingArrays.sort(pq.toArray()). Also, method drainTo can be used to remove some or all elements in priority order and place them in another collection.

Operations on this class make no guarantees about the ordering of elements with equal priority. If you need to enforce an ordering, you can define custom classes or comparators that use a secondary key to break ties in primary priority values. For example, here is a class that applies first-in-first-out tie-breaking to comparable elements. To use it, you would insert anew FIFOEntry(anEntry) instead of a plain entry object.

class FIFOEntry<E extends Comparable<? super E>> implements Comparable<FIFOEntry> { final static AtomicLong seq = new AtomicLong(); final long seqNum; final E entry; public FIFOEntry(E entry) { seqNum = seq.getAndIncrement(); this.entry = entry; } public E getEntry() { return entry; } public int compareTo(FIFOEntry other) { int res = entry.compareTo(other.entry); if (res == 0 && other.entry != this.entry) res = (seqNum < other.seqNum ? -1 : 1); return res; } }

This class is a member of the Java Collections Framework.

Since:

1.5

See Also:

Serialized Form

Constructor Summary
PriorityBlockingQueue() Creates a PriorityBlockingQueue with the default initial capacity (11) that orders its elements according to their natural ordering.
PriorityBlockingQueue(Collection<? extends E> c) Creates a PriorityBlockingQueue containing the elements in the specified collection.
PriorityBlockingQueue(int initialCapacity) Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to theirnatural ordering.
[PriorityBlockingQueue](../../../java/util/concurrent/PriorityBlockingQueue.html#PriorityBlockingQueue%28int, java.util.Comparator%29)(int initialCapacity,Comparator<? super E> comparator) Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to the specified comparator.

Method Summary
boolean	add(E e) Inserts the specified element into this priority queue.
void	clear() Atomically removes all of the elements from this queue.
Comparator<? super E>	comparator() Returns the comparator used to order the elements in this queue, or null if this queue uses the natural ordering of its elements.
boolean	contains(Object o) Returns true if this queue contains the specified element.
int	drainTo(Collection<? super E> c) Removes all available elements from this queue and adds them to the given collection.
int	[drainTo](../../../java/util/concurrent/PriorityBlockingQueue.html#drainTo%28java.util.Collection, int%29)(Collection<? super E> c, int maxElements) Removes at most the given number of available elements from this queue and adds them to the given collection.
Iterator<E>	iterator() Returns an iterator over the elements in this queue.
boolean	offer(E e) Inserts the specified element into this priority queue.
boolean	[offer](../../../java/util/concurrent/PriorityBlockingQueue.html#offer%28E, long, java.util.concurrent.TimeUnit%29)(E e, long timeout,TimeUnit unit) Inserts the specified element into this priority queue.
E	peek() Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
E	poll() Retrieves and removes the head of this queue, or returns null if this queue is empty.
E	[poll](../../../java/util/concurrent/PriorityBlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29)(long timeout,TimeUnit unit) Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
void	put(E e) Inserts the specified element into this priority queue.
int	remainingCapacity() Always returns Integer.MAX_VALUE because a PriorityBlockingQueue is not capacity constrained.
boolean	remove(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 collection.
E	take() Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.
Object[]	toArray() Returns an array containing all of the elements in this queue.
T[]	toArray(T[] a) Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array.
String	toString() Returns a string representation of this collection.

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](../../../java/lang/Object.html#wait%28long, int%29)

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

PriorityBlockingQueue

public PriorityBlockingQueue()

Creates a PriorityBlockingQueue with the default initial capacity (11) that orders its elements according to their natural ordering.

PriorityBlockingQueue

public PriorityBlockingQueue(int initialCapacity)

Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to theirnatural ordering.

Parameters:

initialCapacity - the initial capacity for this priority queue

Throws:

[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if initialCapacity is less than 1

PriorityBlockingQueue

public PriorityBlockingQueue(int initialCapacity, Comparator<? super E> comparator)

Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to the specified comparator.

Parameters:

initialCapacity - the initial capacity for this priority queue

comparator - the comparator that will be used to order this priority queue. If null, the natural ordering of the elements will be used.

Throws:

[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if initialCapacity is less than 1

PriorityBlockingQueue

public PriorityBlockingQueue(Collection<? extends E> c)

Creates a PriorityBlockingQueue containing the elements in the specified collection. If the specified collection is aSortedSet or a PriorityQueue, this priority queue will be ordered according to the same ordering. Otherwise, this priority queue will be ordered according to thenatural ordering of its elements.

Parameters:

c - the collection whose elements are to be placed into this priority queue

Throws:

[ClassCastException](../../../java/lang/ClassCastException.html "class in java.lang") - if elements of the specified collection cannot be compared to one another according to the priority queue's ordering

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified collection or any of its elements are null

Method Detail

add

public boolean add(E e)

Inserts the specified element into this priority queue.

Specified by:

[add](../../../java/util/Collection.html#add%28E%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[add](../../../java/util/concurrent/BlockingQueue.html#add%28E%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[add](../../../java/util/Queue.html#add%28E%29) in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[add](../../../java/util/AbstractQueue.html#add%28E%29) in class [AbstractQueue](../../../java/util/AbstractQueue.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

e - the element to add

Returns:

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

Throws:

[ClassCastException](../../../java/lang/ClassCastException.html "class in java.lang") - if the specified element cannot be compared with elements currently in the priority queue according to the priority queue's ordering

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null

offer

public boolean offer(E e)

Inserts the specified element into this priority queue.

Specified by:

[offer](../../../java/util/concurrent/BlockingQueue.html#offer%28E%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[offer](../../../java/util/Queue.html#offer%28E%29) in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

e - the element to add

Returns:

true (as specified by Queue.offer(E))

Throws:

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null

put

public void put(E e)

Inserts the specified element into this priority queue. As the queue is unbounded this method will never block.

Specified by:

[put](../../../java/util/concurrent/BlockingQueue.html#put%28E%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

e - the element to add

Throws:

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null

offer

public boolean offer(E e, long timeout, TimeUnit unit)

Inserts the specified element into this priority queue. As the queue is unbounded this method will never block.

Specified by:

[offer](../../../java/util/concurrent/BlockingQueue.html#offer%28E, long, java.util.concurrent.TimeUnit%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

e - the element to add

timeout - This parameter is ignored as the method never blocks

unit - This parameter is ignored as the method never blocks

Returns:

true

Throws:

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null

poll

public E poll()

Description copied from interface: [Queue](../../../java/util/Queue.html#poll%28%29)

Retrieves and removes the head of this queue, or returns null if this queue is empty.

Specified by:

[poll](../../../java/util/Queue.html#poll%28%29) in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

the head of this queue, or null if this queue is empty

take

public E take() throws InterruptedException

Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#take%28%29)

Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

Specified by:

[take](../../../java/util/concurrent/BlockingQueue.html#take%28%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

the head of this queue

Throws:

[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang") - if interrupted while waiting

poll

public E poll(long timeout, TimeUnit unit) throws InterruptedException

Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29)

Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.

Specified by:

[poll](../../../java/util/concurrent/BlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

timeout - how long to wait before giving up, in units ofunit

unit - a TimeUnit determining how to interpret thetimeout parameter

Returns:

the head of this queue, or null if the specified waiting time elapses before an element is available

Throws:

[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang") - if interrupted while waiting

peek

public E peek()

Description copied from interface: [Queue](../../../java/util/Queue.html#peek%28%29)

Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.

Specified by:

[peek](../../../java/util/Queue.html#peek%28%29) in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

the head of this queue, or null if this queue is empty

comparator

public Comparator<? super E> comparator()

Returns the comparator used to order the elements in this queue, or null if this queue uses the natural ordering of its elements.

Returns:

the comparator used to order the elements in this queue, or null if this queue uses the natural ordering of its elements

size

public int size()

Description copied from interface: [Collection](../../../java/util/Collection.html#size%28%29)

Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returnsInteger.MAX_VALUE.

Specified by:

[size](../../../java/util/Collection.html#size%28%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[size](../../../java/util/AbstractCollection.html#size%28%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

the number of elements in this collection

remainingCapacity

public int remainingCapacity()

Always returns Integer.MAX_VALUE because a PriorityBlockingQueue is not capacity constrained.

Specified by:

[remainingCapacity](../../../java/util/concurrent/BlockingQueue.html#remainingCapacity%28%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

Integer.MAX_VALUE

remove

public boolean remove(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 and only if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).

Specified by:

[remove](../../../java/util/Collection.html#remove%28java.lang.Object%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[remove](../../../java/util/concurrent/BlockingQueue.html#remove%28java.lang.Object%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[remove](../../../java/util/AbstractCollection.html#remove%28java.lang.Object%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

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(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](../../../java/util/Collection.html#contains%28java.lang.Object%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[contains](../../../java/util/concurrent/BlockingQueue.html#contains%28java.lang.Object%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[contains](../../../java/util/AbstractCollection.html#contains%28java.lang.Object%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

o - object to be checked for containment in this queue

Returns:

true if this queue contains the specified element

toArray

public Object[] toArray()

Returns an array containing all of the elements in this queue. The returned array elements are in no particular order.

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](../../../java/util/Collection.html#toArray%28%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[toArray](../../../java/util/AbstractCollection.html#toArray%28%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

an array containing all of the elements in this queue

toString

public String toString()

Description copied from class: [AbstractCollection](../../../java/util/AbstractCollection.html#toString%28%29)

Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters", " (comma and space). Elements are converted to strings as by String.valueOf(Object).

Overrides:

[toString](../../../java/util/AbstractCollection.html#toString%28%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

a string representation of this collection

drainTo

public int drainTo(Collection<? super E> c)

Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection%29)

Removes all available elements from this queue and adds them to the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result inIllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

Specified by:

[drainTo](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

c - the collection to transfer elements into

Returns:

the number of elements transferred

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if addition of elements is not supported by the specified collection

[ClassCastException](../../../java/lang/ClassCastException.html "class in java.lang") - if the class of an element of this queue prevents it from being added to the specified collection

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified collection is null

[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

drainTo

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

Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection, int%29)

Removes at most the given number of available elements from this queue and adds them to the given collection. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result inIllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

Specified by:

[drainTo](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection, int%29) in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Parameters:

c - the collection to transfer elements into

maxElements - the maximum number of elements to transfer

Returns:

the number of elements transferred

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if addition of elements is not supported by the specified collection

[ClassCastException](../../../java/lang/ClassCastException.html "class in java.lang") - if the class of an element of this queue prevents it from being added to the specified collection

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified collection is null

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](../../../java/util/Collection.html#clear%28%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[clear](../../../java/util/AbstractQueue.html#clear%28%29) in class [AbstractQueue](../../../java/util/AbstractQueue.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

toArray

public T[] toArray(T[] a)

Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. The returned array elements are in no particular order. 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 tonull.

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 totoArray().

Specified by:

[toArray](../../../java/util/Collection.html#toArray%28T[]%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Overrides:

[toArray](../../../java/util/AbstractCollection.html#toArray%28T[]%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

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:

[ArrayStoreException](../../../java/lang/ArrayStoreException.html "class in java.lang") - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if the specified array is null

iterator

public Iterator<E> iterator()

Returns an iterator over the elements in this queue. The iterator does not return the elements in any particular order. 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](../../../java/lang/Iterable.html#iterator%28%29) in interface [Iterable](../../../java/lang/Iterable.html "interface in java.lang")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[iterator](../../../java/util/Collection.html#iterator%28%29) in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Specified by:

[iterator](../../../java/util/AbstractCollection.html#iterator%28%29) in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/PriorityBlockingQueue.html "type parameter in PriorityBlockingQueue")>

Returns:

an iterator over the elements in this queue

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