E - the type of elements held in this collection
public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue <E>
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 Queue which does not permit insertion of null elements, along with methods Queue, Queue, Collection, and Collection. 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.
| Modifier | Constructor and Description |
|---|---|
protected |
AbstractQueue()
Constructor for use by subclasses.
|
| Modifier and Type | Method and Description |
|---|---|
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
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.
|
contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toStringclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitcontains, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, remove, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArraypublic boolean add(E e)
This implementation returns true if offer succeeds, else throws an IllegalStateException.
add in interface
Collection<E>
add in interface
Queue<E>
add in class
AbstractCollection<E>
e - the element to add
Collection.add(E) )
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 E remove()
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.
remove in interface
Queue<E>
NoSuchElementException - if this queue is empty
public E element()
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.
element in interface
Queue<E>
NoSuchElementException - if this queue is empty
public void clear()
This implementation repeatedly invokes poll until it returns null.
public boolean addAll(Collection<? extends E> c)
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.
addAll in interface
Collection<E>
addAll in class
AbstractCollection<E>
c - collection containing elements to be added to this queue
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
add(Object)