programming-for-dummies

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Using Queues
Removing data from a queue
You always remove data from a queue by taking that data off the front of the
queue. The front of the queue always contains the data that’s been stored in
the queue the longest.
In Visual Basic.NET, you can remove and retrieve data off a queue by using
the Dequeue command, as shown in the following Visual Basic.NET example:
Dim LongLine as New Queue
Dim X as Object
LongLine.Enqueue (“My cat”)
LongLine.Enqueue (108.75)
LongLine.Enqueue (“Fat dog”)
X = LongLine.Dequeue
As an alternative to removing data from a queue, you can retrieve data by
using the Peek command. To use the Peek command, you have to assign the
value of the Peek command to a variable like this:
Dim LongLine as New Queue
Dim X as Object
LongLine.Enqueue (“Tasha Korat”)
LongLine.Enqueue (7.25)
LongLine.Enqueue (“Gray”)
X = LongLine.Peek
The preceding code assigns the value “Tasha Korat” to the X variable,
which is declared as an Object data type. (In Visual Basic.NET, an Object
data type can hold any type of data including integers, strings, and decimal
numbers, such as 57.98).
The Peek command only retrieves the data but leaves it at the front of the
queue. Figure 4-6 shows the difference between the Peek and the Dequeue
commands.
Counting and searching a queue
Because a queue can keep growing each time you add more data to it, most
programming languages provide a way to count the total number of items
currently stored in the queue.