Summary: Protected Ctors | Methods | Inherited Methods | [Expand All]

public abstract class

AbstractQueue

extends AbstractCollection<E>
implements Queue<E>

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

Known Direct Subclasses

ArrayBlockingQueue<E>, ConcurrentLinkedQueue<E>, DelayQueue<E extends Delayed>, LinkedBlockingDeque<E>, LinkedBlockingQueue<E>, PriorityBlockingQueue<E>, PriorityQueue<E>, SynchronousQueue<E>

Known Indirect Subclasses

KeepAliveStreamCleaner

Class Overview

This class provides skeletal implementations of some Queue operations. The implementations in this class are appropriate when the base implementation does not allow null elements. Methods add, remove, and element are based on offer, poll, and peek, respectively, but throw exceptions instead of indicating failure via false or null returns.

A Queue implementation that extends this class must minimally define a method offer(E) which does not permit insertion of null elements, along with methods peek(), poll(), size(), and a iterator() supporting remove(). Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassing AbstractCollection.

This class is a member of the Java Collections Framework.

Summary

Protected Constructors
	AbstractQueue() Constructor for use by subclasses.

Public Methods
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.
boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this queue.
void	clear() Removes all of the elements from this queue.
E	element() Retrieves, but does not remove, the head of this queue.
E	remove() Retrieves and removes the head of this queue.

[Expand]

Inherited Methods

From class java.util.AbstractCollection

boolean	add(E e) Ensures that this collection contains the specified element (optional operation). This implementation always throws an `UnsupportedOperationException`.
boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation). This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.
void	clear() Removes all of the elements from this collection (optional operation). This implementation iterates over this collection, removing each element using the `Iterator.remove` operation.
boolean	contains(Object o) Returns `true` if this collection contains the specified element. This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
boolean	containsAll(Collection<?> c) Returns `true` if this collection contains all of the elements in the specified collection. This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection.
boolean	isEmpty() Returns `true` if this collection contains no elements. This implementation returns `size() == 0`.
abstract Iterator<E>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). This implementation iterates over the collection looking for the specified element.
boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
abstract int	size() Returns the number of elements in this collection.
<T> T[]	toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index `0`.
Object[]	toArray() Returns an array containing all of the elements in this collection. This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index `0`.
String	toString() Returns a string representation of this collection.

From class java.lang.Object

Object	clone() Creates and returns a copy of this object.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
final Class<?>	getClass() Returns the runtime class of this `Object`.
int	hashCode() Returns a hash code value for the object.
final void	notify() Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll() Wakes up all threads that are waiting on this object's monitor.
String	toString() Returns a string representation of the object.
final void	wait() Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
final void	wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
final void	wait(long timeout) Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.

From interface java.lang.Iterable

From interface java.util.Collection

abstract boolean	add(E e) Ensures that this collection contains the specified element (optional operation).
abstract boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation).
abstract void	clear() Removes all of the elements from this collection (optional operation).
abstract boolean	contains(Object o) Returns `true` if this collection contains the specified element.
abstract boolean	containsAll(Collection<?> c) Returns `true` if this collection contains all of the elements in the specified collection.
abstract boolean	equals(Object o) Compares the specified object with this collection for equality.
abstract int	hashCode() Returns the hash code value for this collection.
abstract boolean	isEmpty() Returns `true` if this collection contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this collection.
abstract boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation).
abstract boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation).
abstract boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation).
abstract int	size() Returns the number of elements in this collection.
abstract <T> T[]	toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
abstract Object[]	toArray() Returns an array containing all of the elements in this collection.

From interface java.util.Queue

Protected Constructors

protected AbstractQueue ()

Constructor for use by subclasses.

Public Methods

public 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.

This implementation returns true if offer succeeds, else throws an IllegalStateException.

Parameters

e	the element to add

Returns

true (as specified by add(E))

Throws

IllegalStateException	if the element cannot be added at this time due to capacity restrictions
ClassCastException	if the class of the specified element prevents it from being added to this queue
NullPointerException	if the specified element is null and this queue does not permit null elements
IllegalArgumentException	if some property of this element prevents it from being added to this queue

public boolean addAll (Collection<? extends E> c)

Adds all of the elements in the specified collection to this queue. Attempts to addAll of a queue to itself result in IllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

This implementation iterates over the specified collection, and adds each element returned by the iterator to this queue, in turn. A runtime exception encountered while trying to add an element (including, in particular, a null element) may result in only some of the elements having been successfully added when the associated exception is thrown.

Parameters

c	collection containing elements to be added to this queue

Returns

true if this queue changed as a result of the call

Throws

ClassCastException	if the class of an element of the specified collection prevents it from being added to this queue
NullPointerException	if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null
IllegalArgumentException	if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queue
IllegalStateException	if not all the elements can be added at this time due to insertion restrictions

public void clear ()

Removes all of the elements from this queue. The queue will be empty after this call returns.

This implementation repeatedly invokes poll until it returns null.

public E element ()

Retrieves, but does not remove, the head of this queue. This method differs from peek only in that it throws an exception if this queue is empty.

This implementation returns the result of peek unless the queue is empty.

Returns

the head of this queue

Throws

NoSuchElementException	if this queue is empty

public E remove ()

Retrieves and removes the head of this queue. This method differs from poll only in that it throws an exception if this queue is empty.

This implementation returns the result of poll unless the queue is empty.

Returns

the head of this queue

Throws

NoSuchElementException	if this queue is empty

Interfaces

Classes

Enums

Exceptions

Errors

AbstractQueue

Class Overview

Summary

Protected Constructors

protected AbstractQueue ()

Public Methods

public boolean add (E e)

Parameters

Returns

Throws

public boolean addAll (Collection<? extends E> c)

Parameters

Returns

Throws

See Also

public void clear ()

public E element ()

Returns

Throws

public E remove ()

Returns

Throws