Android APIs
public abstract class

AbstractQueue

extends AbstractCollection<E>
implements Queue<E>
java.lang.Object
   ↳ java.util.AbstractCollection<E>
     ↳ java.util.AbstractQueue<E>
Known Direct Subclasses

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 iterator(). Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassing AbstractCollection.

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
From class java.lang.Object
From interface java.util.Collection
From interface java.util.Queue
From interface java.lang.Iterable

Protected Constructors

protected AbstractQueue ()

Added in API level 1

Constructor for use by subclasses.

Public Methods

public boolean add (E e)

Added in API level 1

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 E: the element to add
Returns
boolean 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)

Added in API level 1

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: collection containing elements to be added to this queue
Returns
boolean 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

See also:

public void clear ()

Added in API level 1

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 ()

Added in API level 1

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
E the head of this queue
Throws
NoSuchElementException if this queue is empty

public E remove ()

Added in API level 1

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
E the head of this queue
Throws
NoSuchElementException if this queue is empty