AbstractQueue
abstract class AbstractQueue<E : Any!> : AbstractCollection<E>, Queue<E>
kotlin.Any | ||
↳ | java.util.AbstractCollection<E> | |
↳ | java.util.AbstractQueue |
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 Queue#offer
which does not permit insertion of null
elements, along with methods java.util.Queue#peek
, Queue#poll
, Collection#size
, and Collection#iterator
. Typically, additional methods will be overridden as well. If these requirements cannot be met, consider instead subclassing AbstractCollection
.
Summary
Protected constructors | |
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Constructor for use by subclasses. |
Public methods | |
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open Boolean |
add(element: E) Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning |
open Boolean |
addAll(elements: Collection<E>) Adds all of the elements in the specified collection to this queue. |
open Unit |
clear() Removes all of the elements from this queue. |
open E |
element() Retrieves, but does not remove, the head of this queue. |
open E |
remove() Retrieves and removes the head of this queue. |
Inherited functions | |
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Inherited properties | |
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Protected constructors
Public methods
add
open fun add(element: E): Boolean
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 |
Return | |
---|---|
Boolean |
true (as specified by Collection#add ) |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the add operation is not supported by this collection |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this queue |
java.lang.NullPointerException |
if the specified element is null and this queue does not permit null elements |
java.lang.IllegalArgumentException |
if some property of this element prevents it from being added to this queue |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
addAll
open fun addAll(elements: Collection<E>): Boolean
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 |
Return | |
---|---|
Boolean |
true if this queue changed as a result of the call |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the addAll operation is not supported by this collection |
java.lang.ClassCastException |
if the class of an element of the specified collection prevents it from being added to this queue |
java.lang.NullPointerException |
if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null |
java.lang.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 |
java.lang.IllegalStateException |
if not all the elements can be added at this time due to insertion restrictions |
See Also
clear
open fun clear(): Unit
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
.
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the clear operation is not supported by this collection |
element
open fun element(): E
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.
Return | |
---|---|
E |
the head of this queue |
Exceptions | |
---|---|
java.util.NoSuchElementException |
if this queue is empty |
remove
open fun remove(): E
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.
Return | |
---|---|
E |
the head of this queue |
Exceptions | |
---|---|
java.util.NoSuchElementException |
if this queue is empty |