Queue Class
Represents a first-in, first-out collection of objects.
Assembly: mscorlib (in mscorlib.dll)
The Queue type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() | Queue() | Initializes a new instance of the Queue class that is empty, has the default initial capacity, and uses the default growth factor. |
![]() ![]() | Queue(ICollection) | Initializes a new instance of the Queue class that contains elements copied from the specified collection, has the same initial capacity as the number of elements copied, and uses the default growth factor. |
![]() ![]() | Queue(Int32) | Initializes a new instance of the Queue class that is empty, has the specified initial capacity, and uses the default growth factor. |
![]() ![]() | Queue(Int32, Single) | Initializes a new instance of the Queue class that is empty, has the specified initial capacity, and uses the specified growth factor. |
| Name | Description | |
|---|---|---|
![]() ![]() | Count | Gets the number of elements contained in the Queue. |
![]() ![]() | IsSynchronized | Gets a value indicating whether access to the Queue is synchronized (thread safe). |
![]() ![]() | SyncRoot | Gets an object that can be used to synchronize access to the Queue. |
| Name | Description | |
|---|---|---|
![]() ![]() | Clear | Removes all objects from the Queue. |
![]() ![]() | Clone | Creates a shallow copy of the Queue. |
![]() ![]() | Contains | Determines whether an element is in the Queue. |
![]() ![]() | CopyTo | Copies the Queue elements to an existing one-dimensional Array, starting at the specified array index. |
![]() ![]() | Dequeue | Removes and returns the object at the beginning of the Queue. |
![]() ![]() | Enqueue | Adds an object to the end of the Queue. |
![]() ![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() ![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() ![]() | GetEnumerator | Returns an enumerator that iterates through the Queue. |
![]() ![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() ![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() ![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() ![]() | Peek | Returns the object at the beginning of the Queue without removing it. |
![]() ![]() | Synchronized | Returns a Queue wrapper that is synchronized (thread safe). |
![]() ![]() | ToArray | Copies the Queue elements to a new array. |
![]() ![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
![]() ![]() | TrimToSize | Sets the capacity to the actual number of elements in the Queue. |
| Name | Description | |
|---|---|---|
![]() | AsParallel | Enables parallelization of a query. (Defined by ParallelEnumerable.) |
![]() | AsQueryable | Converts an IEnumerable to an IQueryable. (Defined by Queryable.) |
![]() ![]() | Cast<TResult> | Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.) |
![]() ![]() | OfType<TResult> | Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.) |
Queues are useful for storing messages in the order they were received for sequential processing. This class implements a queue as a circular array. Objects stored in a Queue are inserted at one end and removed from the other.
The capacity of a Queue is the number of elements the Queue can hold. As elements are added to a Queue, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize.
The growth factor is the number by which the current capacity is multiplied when a greater capacity is required. The growth factor is determined when the Queue is constructed. The default growth factor is 2.0. The capacity of the Queue will always increase by at least a minimum of four, regardless of the growth factor. For example, a Queue with a growth factor of 1.0 will always increase in capacity by four when a greater capacity is required.
Queue accepts nullptr as a valid value and allows duplicate elements.
For the generic version of this collection, see System.Collections.Generic::Queue<T>
The following example shows how to create and add values to a Queue and how to print out its values.
using namespace System; using namespace System::Collections; void PrintValues( IEnumerable^ myCollection ); int main() { // Creates and initializes a new Queue. Queue^ myQ = gcnew Queue; myQ->Enqueue( "Hello" ); myQ->Enqueue( "World" ); myQ->Enqueue( "!" ); // Displays the properties and values of the Queue. Console::WriteLine( "myQ" ); Console::WriteLine( "\tCount: {0}", myQ->Count ); Console::Write( "\tValues:" ); PrintValues( myQ ); } void PrintValues( IEnumerable^ myCollection ) { IEnumerator^ myEnum = myCollection->GetEnumerator(); while ( myEnum->MoveNext() ) { Object^ obj = safe_cast<Object^>(myEnum->Current); Console::Write( " {0}", obj ); } Console::WriteLine(); } /* This code produces the following output. myQ Count: 3 Values: Hello World ! */
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
To guarantee the thread safety of the Queue, all operations must be done through the wrapper returned by the Synchronized method.
Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.
