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Added in API level 1

public class

PriorityQueue

extends AbstractQueue<E>
implements Serializable

java.lang.Object
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractQueue<E>
		↳	java.util.PriorityQueue<E>

Class Overview

A PriorityQueue holds elements on a priority heap, which orders the elements according to their natural order or according to the comparator specified at construction time. If the queue uses natural ordering, only elements that are comparable are permitted to be inserted into the queue.

The least element of the specified ordering is stored at the head of the queue and the greatest element is stored at the tail of the queue.

A PriorityQueue is not synchronized. If multiple threads will have to access it concurrently, use the PriorityBlockingQueue.

Summary

Public Constructors
	PriorityQueue() Constructs a priority queue with an initial capacity of 11 and natural ordering.
	PriorityQueue(int initialCapacity) Constructs a priority queue with the specified capacity and natural ordering.
	PriorityQueue(int initialCapacity, Comparator<? super E> comparator) Constructs a priority queue with the specified capacity and comparator.
	PriorityQueue( Collection<? extends E> c) Constructs a priority queue that contains the elements of a collection.
	PriorityQueue( PriorityQueue<? extends E> c) Constructs a priority queue that contains the elements of another priority queue.
	PriorityQueue( SortedSet<? extends E> c) Constructs a priority queue that contains the elements of a sorted set.

Public Methods
boolean	add(E o) Adds the specified object to the priority queue.
void	clear() Removes all the elements of the priority queue.
Comparator<? super E>	comparator() Gets the comparator of the priority queue.
Iterator<E>	iterator() Gets the iterator of the priority queue, which will not return elements in any specified ordering.
boolean	offer(E o) Inserts the element to the priority queue.
E	peek() Gets but does not remove the head of the queue.
E	poll() Gets and removes the head of the queue.
boolean	remove( Object o) Removes the specified object from the priority queue.
int	size() Gets the size of the priority queue.

[Expand]

Inherited Methods

From class java.util.AbstractQueue

From class java.util.AbstractCollection

boolean	add(E object) Attempts to add `object` to the contents of this `Collection` (optional).
boolean	addAll( Collection<? extends E> collection) Attempts to add all of the objects contained in `collection` to the contents of this `Collection` (optional).
void	clear() Removes all elements from this `Collection`, leaving it empty (optional).
boolean	contains( Object object) Tests whether this `Collection` contains the specified object.
boolean	containsAll( Collection<?> collection) Tests whether this `Collection` contains all objects contained in the specified `Collection`.
boolean	isEmpty() Returns if this `Collection` contains no elements.
abstract Iterator<E>	iterator() Returns an instance of `Iterator` that may be used to access the objects contained by this `Collection`.
boolean	remove( Object object) Removes one instance of the specified object from this `Collection` if one is contained (optional).
boolean	removeAll( Collection<?> collection) Removes all occurrences in this `Collection` of each object in the specified `Collection` (optional).
boolean	retainAll( Collection<?> collection) Removes all objects from this `Collection` that are not also found in the `Collection` passed (optional).
abstract int	size() Returns a count of how many objects this `Collection` contains.
<T> T[]	toArray(T[] contents) Returns an array containing all elements contained in this `Collection`.
Object[]	toArray() Returns a new array containing all elements contained in this `Collection`.
String	toString() Returns the string representation of this `Collection`.

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals( Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

From interface java.lang.Iterable

From interface java.util.Collection

abstract boolean	add(E object) Attempts to add `object` to the contents of this `Collection` (optional).
abstract boolean	addAll( Collection<? extends E> collection) Attempts to add all of the objects contained in `Collection` to the contents of this `Collection` (optional).
abstract void	clear() Removes all elements from this `Collection`, leaving it empty (optional).
abstract boolean	contains( Object object) Tests whether this `Collection` contains the specified object.
abstract boolean	containsAll( Collection<?> collection) Tests whether this `Collection` contains all objects contained in the specified `Collection`.
abstract boolean	equals( Object object) Compares the argument to the receiver, and returns true if they represent the same object using a class specific comparison.
abstract int	hashCode() Returns an integer hash code for the receiver.
abstract boolean	isEmpty() Returns if this `Collection` contains no elements.
abstract Iterator<E>	iterator() Returns an instance of `Iterator` that may be used to access the objects contained by this `Collection`.
abstract boolean	remove( Object object) Removes one instance of the specified object from this `Collection` if one is contained (optional).
abstract boolean	removeAll( Collection<?> collection) Removes all occurrences in this `Collection` of each object in the specified `Collection` (optional).
abstract boolean	retainAll( Collection<?> collection) Removes all objects from this `Collection` that are not also found in the `Collection` passed (optional).
abstract int	size() Returns a count of how many objects this `Collection` contains.
abstract <T> T[]	toArray(T[] array) Returns an array containing all elements contained in this `Collection`.
abstract Object[]	toArray() Returns a new array containing all elements contained in this `Collection`.

From interface java.util.Queue

abstract boolean	add(E e) Inserts the specified element into this queue 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.
abstract E	element() Retrieves, but does not remove, the head of this queue.
abstract boolean	offer(E e) Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions.
abstract E	peek() Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.
abstract E	poll() Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
abstract E	remove() Retrieves and removes the head of this queue.

Public Constructors

public PriorityQueue ()

Added in API level 1

Constructs a priority queue with an initial capacity of 11 and natural ordering.

public PriorityQueue (int initialCapacity)

Added in API level 1

Constructs a priority queue with the specified capacity and natural ordering.

Parameters

initialCapacity	the specified capacity.

Throws

IllegalArgumentException	if the initialCapacity is less than 1.

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

Added in API level 1

Constructs a priority queue with the specified capacity and comparator.

Parameters

initialCapacity	the specified capacity.
comparator	the specified comparator. If it is null, the natural ordering will be used.

Throws

IllegalArgumentException	if the initialCapacity is less than 1.

public PriorityQueue (Collection<? extends E> c)

Added in API level 1

Constructs a priority queue that contains the elements of a collection. The constructed priority queue has the initial capacity of 110% of the size of the collection. The queue uses natural ordering to order its elements.

Parameters

c	the collection whose elements will be added to the priority queue to be constructed.

Throws

ClassCastException	if any of the elements in the collection are not comparable.
NullPointerException	if any of the elements in the collection are null.

public PriorityQueue (PriorityQueue<? extends E> c)

Added in API level 1

Constructs a priority queue that contains the elements of another priority queue. The constructed priority queue has the initial capacity of 110% of the specified one. Both priority queues have the same comparator.

Parameters

c	the priority queue whose elements will be added to the priority queue to be constructed.

public PriorityQueue (SortedSet<? extends E> c)

Added in API level 1

Constructs a priority queue that contains the elements of a sorted set. The constructed priority queue has the initial capacity of 110% of the size of the sorted set. The priority queue will have the same comparator as the sorted set.

Parameters

c	the sorted set whose elements will be added to the priority queue to be constructed.

Public Methods

public boolean add (E o)

Added in API level 1

Adds the specified object to the priority queue.

Parameters

o	the object to be added.

Returns

always true.

Throws

ClassCastException	if the element cannot be compared with the elements in the priority queue using the ordering of the priority queue.
NullPointerException	if `o` is `null`.

public void clear ()

Added in API level 1

Removes all the elements of the priority queue.

public Comparator<? super E> comparator ()

Added in API level 1

Gets the comparator of the priority queue.

Returns

the comparator of the priority queue or null if the natural ordering is used.

public Iterator<E> iterator ()

Added in API level 1

Gets the iterator of the priority queue, which will not return elements in any specified ordering.

Returns

the iterator of the priority queue.

public boolean offer (E o)

Added in API level 1

Inserts the element to the priority queue.

Parameters

o	the element to add to the priority queue.

Returns

always true

Throws

ClassCastException	if the element cannot be compared with the elements in the priority queue using the ordering of the priority queue.
NullPointerException	if `o` is `null`.

public E peek ()

Added in API level 1

Gets but does not remove the head of the queue.

Returns

the head of the queue or null if the queue is empty.

public E poll ()

Added in API level 1

Gets and removes the head of the queue.

Returns

the head of the queue or null if the queue is empty.

public boolean remove (Object o)

Added in API level 1

Removes the specified object from the priority queue.

Parameters

o	the object to be removed.

Returns

true if the object was in the priority queue, false if the object was not in the priority queue.

public int size ()

Added in API level 1

Gets the size of the priority queue. If the size of the queue is greater than the Integer.MAX, then it returns Integer.MAX.

Returns

the size of the priority queue.

information

No examples for this method.

Frequently called with: [Clear]

This example was provided by APIMiner.

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PriorityQueue

Class Overview

Summary

Public Constructors

public PriorityQueue ()

public PriorityQueue (int initialCapacity)

Parameters

Throws

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

Parameters

Throws

public PriorityQueue (Collection<? extends E> c)

Parameters

Throws

public PriorityQueue (PriorityQueue<? extends E> c)

Parameters

public PriorityQueue (SortedSet<? extends E> c)

Parameters

Public Methods

public boolean add (E o)

Parameters

Returns

Throws

public void clear ()

public Comparator<? super E> comparator ()

Returns

public Iterator<E> iterator ()

Returns

public boolean offer (E o)

Parameters

Returns

Throws

public E peek ()

Returns

public E poll ()

Returns

public boolean remove (Object o)

Parameters

Returns

public int size ()

Returns