public abstract class AbstractQueue<E>

  1. Object
  2. AbstractCollection<E>
  3. AbstractQueue

ImplementsCollection<E>, Iterable<E>, Queue<E>

Known subtypesPriorityQueue

AbstractQueue is an abstract class which implements some of the methods in Queue. The provided implementations of add, remove and element are based on offer, poll, and peek except that they throw exceptions to indicate some error instead of returning true or false.

Type parameter E: the type of the element in the collection.

Constructors

protected AbstractQueue()Constructor to be used by subclasses.

Methods

public boolean add(E o)Adds an element to the queue.
public boolean addAll(Collection<? extends E> c)Adds all the elements of a collection to the queue.
public E remove()Removes the element at the head of the queue and returns it.
public E element()Returns but does not remove the element at the head of the queue.
public void clear()Removes all elements of the queue, leaving it empty.

Inherited methods

From AbstractCollection

contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toString, toArray, toArray

From Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait, clone

From Collection

removeIf

From Iterable

forEach

From Queue

offer, poll, peek

Constructor details

AbstractQueue

protected AbstractQueue()
Constructor to be used by subclasses.

Method details

add

public boolean add(E o)
Adds an element to the queue.

Parameters

o E
the element to be added to the queue.

Returns

true if the operation succeeds, otherwise false.

Throws

IllegalStateException
if the element is not allowed to be added to the queue.

addAll

public boolean addAll(Collection<? extends E> c)
Adds all the elements of a collection to the queue. If the collection is the queue itself, then an IllegalArgumentException will be thrown. If during the process, some runtime exception is thrown, then those elements in the collection which have already successfully been added will remain in the queue. The result of the method is undefined if the collection is modified during the process of the method.

Parameters

c Collection<? extends E>
the collection to be added to the queue.

Returns

true if the operation succeeds, otherwise false.

Throws

NullPointerException
if the collection or any element of it is null.
IllegalArgumentException
If the collection to be added to the queue is the queue itself.

remove

public E remove()
Removes the element at the head of the queue and returns it.

Returns

the element at the head of the queue.

Throws

NoSuchElementException
if the queue is empty.

element

public E element()
Returns but does not remove the element at the head of the queue.

Returns

the element at the head of the queue.

Throws

NoSuchElementException
if the queue is empty.

clear

public void clear()
Removes all elements of the queue, leaving it empty.

Throws

UnsupportedOperationException
it the iterator does not support removing elements from this Collection