java.util

Class AbstractQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

Type Parameters:

E - the type of the element in the collection.

All Implemented Interfaces:

Iterable<E>, Collection<E>, Queue<E>

Direct Known Subclasses:

PriorityQueue

public abstract class AbstractQueue<E>
extends AbstractCollection<E>
implements Queue<E>

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.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractQueue() Constructor to be used by subclasses.

Method Summary

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

Methods inherited from class java.util.AbstractCollection

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Queue

offer, peek, poll

Methods inherited from interface java.util.Collection

contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

Constructor Detail

AbstractQueue

protected AbstractQueue()

Constructor to be used by subclasses.

Method Detail

add

public boolean add(E o)

Adds an element to the queue.

Specified by:

add in interface Collection<E>

Overrides:

add in class AbstractCollection<E>

Parameters:

o - 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.

Specified by:

addAll in interface Collection<E>

Overrides:

addAll in class AbstractCollection<E>

Parameters:

c - 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.

Specified by:

remove in interface Queue<E>

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.

Specified by:

element in interface Queue<E>

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.

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractCollection<E>

See Also:

AbstractCollection.iterator(), AbstractCollection.isEmpty(), AbstractCollection.size()