C# 5.0 Programmer's Reference

334 ❘ CHAPTER 14 Collection Classes
(continued)
Property/Method
Count
Dequeue
Enqueue
Peek
ToArray
TrimToSize
Purpose
Returns the number of items in the Queue.
Returns and removes the item at the front of the Queue.
Adds an item to the back of the Queue.
Returns a reference to the item at the front of the Queue without
removing it.
Returns a one-dimensional array containing references to the objects
in the Queue. The item at the front of the Queue is placed first in
the array.
Frees any empty space in the Queue.
Like Stacks, Queues must resize themselves if they become full and that slows things down. Also like
Stacks, Queues provide overloaded constructors that let you determine how big the Queue is initially.
The first constructor takes no parameters and allocates a default initial capacity. If the Queue is full,
it enlarges itself by a default growth factor.
The second constructor takes as a parameter the Queue’s initial capacity. If you know that you will
add 1,000 items to the Queue, you can save some time by initially allocating room for 1,000 items.
With this constructor, the Queue also uses a default growth factor.
The third constructor takes as a parameter an object that implements the ICollection interface. The
constructor allocates enough room to hold the items in the ICollection and copies them into the
Queue. This version also uses a default growth factor.
The final version of the constructor takes as parameters an initial capacity and a growth factor
between 1.0 and 10.0. A larger growth factor means the Queue resizes itself less often, but also
means it may contain a lot of unused space.
The following short example demonstrates a Queue.
Queue queue = new Queue();
queue.Enqueue("Apple");
queue.Enqueue("Banana");
queue.Enqueue("Cherry");
Console.WriteLine(queue.Dequeue());
Console.WriteLine(queue.Dequeue());
Console.WriteLine(queue.Dequeue());
This code creates a Queue and adds three strings to it. It then dequeues the three values, displaying
the results in the Console window. The following text shows the results.
Apple
Banana
Cherry
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