IQueue Interface

Reference

Definition

Namespace:: Java.Util

Assembly:: Mono.Android.dll

Important

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A collection designed for holding elements prior to processing.

[Android.Runtime.Register("java/util/Queue", "", "Java.Util.IQueueInvoker")]
[Java.Interop.JavaTypeParameters(new System.String[] { "E" })]
public interface IQueue : IDisposable, Java.Interop.IJavaPeerable, Java.Util.ICollection

[<Android.Runtime.Register("java/util/Queue", "", "Java.Util.IQueueInvoker")>]
[<Java.Interop.JavaTypeParameters(new System.String[] { "E" })>]
type IQueue = interface
    interface ICollection
    interface IIterable
    interface IJavaObject
    interface IDisposable
    interface IJavaPeerable

Derived: Java.Util.AbstractQueue

Java.Util.ArrayDeque

Java.Util.Concurrent.ArrayBlockingQueue

Java.Util.Concurrent.ConcurrentLinkedDeque

Java.Util.Concurrent.ConcurrentLinkedQueue

More…

Attributes: RegisterAttribute JavaTypeParametersAttribute

Implements: IJavaObject IJavaPeerable IIterable ICollection IDisposable

Remarks

A collection designed for holding elements prior to processing. Besides basic Collection operations, queues provide additional insertion, extraction, and inspection operations. Each of these methods exists in two forms: one throws an exception if the operation fails, the other returns a special value (either null or false, depending on the operation). The latter form of the insert operation is designed specifically for use with capacity-restricted Queue implementations; in most implementations, insert operations cannot fail.

<table class="striped"> <caption>Summary of Queue methods</caption> <thead> <tr> <td></td> <th scope="col" style="font-weight:normal; font-style:italic">Throws exception</th> <th scope="col" style="font-weight:normal; font-style:italic">Returns special value</th> </tr> </thead> <tbody> <tr> <th scope="row">Insert</th> <td>#add(Object) add(e)</td> <td>#offer(Object) offer(e)</td> </tr> <tr> <th scope="row">Remove</th> <td>#remove() remove()</td> <td>#poll() poll()</td> </tr> <tr> <th scope="row">Examine</th> <td>#element() element()</td> <td>#peek() peek()</td> </tr> </tbody> </table>

Queues typically, but do not necessarily, order elements in a FIFO (first-in-first-out) manner. Among the exceptions are priority queues, which order elements according to a supplied comparator, or the elements' natural ordering, and LIFO queues (or stacks) which order the elements LIFO (last-in-first-out). Whatever the ordering used, the <em>head</em> of the queue is that element which would be removed by a call to #remove() or #poll(). In a FIFO queue, all new elements are inserted at the <em>tail</em> of the queue. Other kinds of queues may use different placement rules. Every Queue implementation must specify its ordering properties.

The #offer offer method inserts an element if possible, otherwise returning false. This differs from the java.util.Collection#add Collection.add method, which can fail to add an element only by throwing an unchecked exception. The offer method is designed for use when failure is a normal, rather than exceptional occurrence, for example, in fixed-capacity (or "bounded") queues.

The #remove() and #poll() methods remove and return the head of the queue. Exactly which element is removed from the queue is a function of the queue's ordering policy, which differs from implementation to implementation. The remove() and poll() methods differ only in their behavior when the queue is empty: the remove() method throws an exception, while the poll() method returns null.

The #element() and #peek() methods return, but do not remove, the head of the queue.

The Queue interface does not define the blocking queue methods, which are common in concurrent programming. These methods, which wait for elements to appear or for space to become available, are defined in the java.util.concurrent.BlockingQueue interface, which extends this interface.

Queue implementations generally do not allow insertion of null elements, although some implementations, such as LinkedList, do not prohibit insertion of null. Even in the implementations that permit it, null should not be inserted into a Queue, as null is also used as a special return value by the poll method to indicate that the queue contains no elements.

Queue implementations generally do not define element-based versions of methods equals and hashCode but instead inherit the identity based versions from class Object, because element-based equality is not always well-defined for queues with the same elements but different ordering properties.

Added in 1.5.

Java documentation for java.util.Queue.

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.

Properties

Handle	Gets the JNI value of the underlying Android object. (Inherited from IJavaObject)
IsEmpty	Returns if this `Collection` contains no elements. (Inherited from ICollection)
JniIdentityHashCode	Returns the value of `java.lang.System.identityHashCode()` for the wrapped instance. (Inherited from IJavaPeerable)
JniManagedPeerState	State of the managed peer. (Inherited from IJavaPeerable)
JniPeerMembers	Member access and invocation support. (Inherited from IJavaPeerable)
PeerReference	Returns a JniObjectReference of the wrapped Java object instance. (Inherited from IJavaPeerable)

Methods

Add(Object)	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.
AddAll(ICollection)	Adds all of the elements in the specified collection to this collection (optional operation). (Inherited from ICollection)
Clear()	Removes all of the elements from this collection (optional operation). (Inherited from ICollection)
Contains(Object)	Returns `true` if this collection contains the specified element. (Inherited from ICollection)
ContainsAll(ICollection)	Returns `true` if this collection contains all of the elements in the specified collection. (Inherited from ICollection)
Disposed()	Called when the instance has been disposed. (Inherited from IJavaPeerable)
DisposeUnlessReferenced()	If there are no outstanding references to this instance, then calls `Dispose()`; otherwise, does nothing. (Inherited from IJavaPeerable)
Element()	Retrieves, but does not remove, the head of this queue.
Equals(Object)	Compares the specified object with this collection for equality. (Inherited from ICollection)
Finalized()	Called when the instance has been finalized. (Inherited from IJavaPeerable)
ForEach(IConsumer)	Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception. (Inherited from IIterable)
GetHashCode()	Returns the hash code value for this collection. (Inherited from ICollection)
Iterator()	Returns an iterator over the elements in this collection. (Inherited from ICollection)
Offer(Object)	Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions.
Peek()	Retrieves, but does not remove, the head of this queue, or returns `null` if this queue is empty.
Poll()	Retrieves and removes the head of this queue, or returns `null` if this queue is empty.
Remove()	Retrieves and removes the head of this queue.
Remove(Object)	Removes a single instance of the specified element from this collection, if it is present (optional operation). (Inherited from ICollection)
RemoveAll(ICollection)	Removes all of this collection's elements that are also contained in the specified collection (optional operation). (Inherited from ICollection)
RemoveIf(IPredicate)	Removes all of the elements of this collection that satisfy the given predicate. (Inherited from ICollection)
RetainAll(ICollection)	Retains only the elements in this collection that are contained in the specified collection (optional operation). (Inherited from ICollection)
SetJniIdentityHashCode(Int32)	Set the value returned by `JniIdentityHashCode`. (Inherited from IJavaPeerable)
SetJniManagedPeerState(JniManagedPeerStates)	(Inherited from IJavaPeerable)
SetPeerReference(JniObjectReference)	Set the value returned by `PeerReference`. (Inherited from IJavaPeerable)
Size()	Returns the number of elements in this collection. (Inherited from ICollection)
Spliterator()	Creates a `Spliterator` over the elements described by this `Iterable`. (Inherited from IIterable)
ToArray()	Returns an array containing all of the elements in this collection. (Inherited from ICollection)
ToArray(IIntFunction)	Returns an array containing all of the elements in this collection, using the provided `generator` function to allocate the returned array. (Inherited from ICollection)
ToArray(Object[])	Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. (Inherited from ICollection)
UnregisterFromRuntime()	Unregister this instance so that the runtime will not return it from future Java.Interop.JniRuntime+JniValueManager.PeekValue invocations. (Inherited from IJavaPeerable)

Explicit Interface Implementations

IIterable.Spliterator()

Creates a Spliterator over the elements in this collection.

(Inherited from ICollection)

Extension Methods

JavaCast<TResult>(IJavaObject)	Performs an Android runtime-checked type conversion.
JavaCast<TResult>(IJavaObject)
GetJniTypeName(IJavaPeerable)
ToEnumerable(IIterable)
ToEnumerable<T>(IIterable)

Applies to

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