The Queue class represents a first-in, first-out collection of objects. It implements a queue as a circular array. Objects stored in a Queue are inserted at one end and removed from the other.
Three main operations can be performed on a Queue and its elements:
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 following are basic methods of the Queue class.
| Method | Description |
|---|---|
Clear() |
Removes all objects from the Queue. |
Clone() |
Creates a shallow copy of the Queue. |
Contains(Object) |
Determines whether an element is in the Queue. |
CopyTo(Array, Int32) |
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(Object) |
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) |
GetEnumerator() |
Returns an enumerator that iterates through the Queue. |
GetHashCode() |
Serves as the default hash function. (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(Queue) |
Returns a new Queue that wraps the original queue, and is 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. |
The following example shows how to create and add values to a Queue and how to print out its values.
Public Sub Example()
Dim myQ As Queue = New Queue()
myQ.Enqueue("Hello")
myQ.Enqueue("World")
myQ.Enqueue("!")
Console.WriteLine("myQ")
Console.WriteLine(vbTab & "Count: {0}", myQ.Count)
Console.Write(vbTab & "Values:")
For Each obj As Object In myQ
Console.Write(" {0}", obj)
Next
Console.WriteLine()
End Sub
Let's run the above code, and you will see the following output.
myQ
Count: 3
Values: Hello World !