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Part 82 Generic queue collection class Video Lecture - C sharp Enhance
Text Transcript from Video
this part 82 of c-sharp tutorial in this
video we'll discuss the generic queue
collection class queue is a generic
first-in first-out collection class
that's present in system door collection
store generic namespace that is the
order in which we add items to the queue
the same order will be used to retrieve
items from the queue the SKU collection
class is analogous to a queue at the ATM
machine to withdraw money the order in
which people QR will be the order in
which they will be able to get out of
the queue and withdraw money from the
ATM this queue collection class also
operates in a similar fashion the first
item to be added to the queue will be
the first item to be removed from the
queue let's understand the SKU
collection class with an example we'll
be using this customer class and this
demo and notice that this is
straightforward with three auto
implemented properties within our main
method we are creating five instances of
this customer class customer one through
customer five first of all let's go
ahead and create an instance of this
queue class so queue and what type of
queue do we want to create we want to
create a queue of customers the type
here is going to be customer and let's
give it a meaningful name let's call it
Q customers and just like how we can
specify an initial capacity of a list
and a dictionary we can also specify the
initial capacity of the queue using this
overloaded version of the constructor
but let's use the default constructor
that doesn't expect any parameters and
then to add items to a list we use add
method similarly to add items to a
dictionary we use add method but then to
add items to a queue we use NQ method so
let's go ahead and use that NQ method
and add an item to this queue so let's
add customer one object at the moment
there are no elements within this queue
so this customer one object will be the
first item within the queue let's now
add customer to object
so where will this customer to object we
added this customer to object will be
added at the end of the queue meaning
after customer one object so what is the
send queue method going to do look at
the intelligence it adds an object to
the end of the queue so these objects
will be queued one after another so
similarly let's add customer three
customer four and customer five all
right so these customer objects will be
n queued in that order one after another
because every time you invoke an NQ
method and then pass it an object that
object will be added at the end of the
queue now to retrieve an item from a
list we use you know its index the items
index within that list and similarly to
retrieve an item from a dictionary we
use the items key but then to retrieve
an item from a queue we use DQ method so
queue customers dot DQ and look at the
intelligence what is it returning back
it's returning a customer object back
because this Q is of is a collection of
type customer objects and then look at
what it is doing it is going to remove
and return the object at the beginning
of the queue okay so if you retrieve an
item from a dictionary by its key you
know it returns that item but then the
item will still be there in that
dictionary similarly if you retrieve an
item from the list using its index you
know it returns the item at that index
position but then the item is still
going to be present within the list but
then if you use this DQ method you know
the item that is present at the
beginning of the queue will be removed
from the queue and then returned okay so
let's store the item in a variable of
type customer and maybe let's call it c1
and let's say we want to print the
customers ID and name
so C 1 dot ID
and we want to print their name as well
so see one dot name so this DQ method is
going to remove and return the item so
after the first customer object is DQ'd
let's find out the total count of items
that are available still in the queue
and to find the total number of elements
that are available that are present in a
queue we can use the count property just
like how we have used it with lists and
dictionary collection classes so let's
say console.writeline total items in the
queue so queue dictionary queue
customers dot count and again we can
either use this count property I use
this link extension method we have seen
how to use this link extension method
with the list and dictionary so we would
use that in a same fashion with the
queue as well so let's use the count
property all right so let's go ahead and
run this now okay so look at that
if the output that we get but the
customer ID is 1 0 1 and name is mark
and if you remember you know this
customer 1 object has caught an ID of 1
0 1 and name is Mark so when we use this
DQ method since customer 1 object is the
first item that is present at the
beginning of the queue that's what will
be DQ'd ok now let's go ahead and DQ one
after another you know let's try and dig
you all these customer customers from
the queue and to speed things up I have
all the day types and code so let me
copy and paste that right here and this
code is very much similar to what we
have here so basically we are retrieving
customer to customer 3 customer 4 and
customer fired all the customers ok so
let's go ahead and run this and look at
this as vdq customers the count also
keeps reducing ok all right so what is
the purpose of DQ method it's going to
remove and return an item that is
present at the beginning of the queue
and to add elements to the queue we use
NQ method okay now is it possible to
loop through each item that is present
within the queue absolutely we can use
for each loop just like how we can use
you know the for each loop with other
collection classes like list and
dictionary in a similar fashion we can
also use it with our queue collection
class so for each customer let's call it
maybe see in customers queue customers
so let's go ahead and print their ID and
name and then the total items that are
left with in the queue so here the
reference variable is C so let's go
ahead and change that SC all right and
let's get rid of this piece of code so
basically at the moment within the queue
we have these five elements and then we
are using a for each loop to iterate
through the items within the queue okay
so let's go ahead and run that and look
at that you know it iterates through all
the customers within the queue and then
look at that the total count is still 5
as it is iterating through because the
for each loop will not remove the items
from the queue it simply iterates
through them and then in this case we
are printing their ID and name and then
the total items within the queue all
right now we know that the DQ method is
going to remove and return the item that
is present at the beginning of the queue
is it possible to return the item that
is present at the beginning of the queue
without removing it absolutely and for
that purpose we have a method called
peek so let's go ahead and use that
method look at that
when I say queue customer is dot peek
look at you know what the intercept
intelligence says this method returns
the object at the beginning of the queue
without removing it so let's get this
customer object out that is present at
the beginning of the queue and maybe
let's store in this variable C and then
let's go ahead and print
a ID and name okay so all we are doing
here is using the peek method to return
the item that is present at the
beginning of the queue we are printing
their ID and name and then we are also
printing the total count so let's go
ahead and run this okay
look at that we get the first item that
is present at the queue and look at the
total count it is still 5 so peak method
is going to return the item that is
present at the beginning of the queue
without removing it ok so that's the
basic difference you know DQ method is
going to remove and return it
whereas peak method is going to return
that without removing ok now what's
going to happen if I copy this piece of
code paste it here and look at that we
are calling peak method again again
let's call this reference variable C 2
okay now so here it's going to return
the object that is present at the
beginning of the queue which is customer
1 if I invoke a peak method again will
it return customer 1 object or customer
2 object it will return still customer 1
object because that is present at the
beginning of the queue and it's not
removed so no matter how many times you
call this peak method you are still
going to get the same object which is
customer 1 because that is still present
at the beginning of the queue alright
now how to check if a specific item
exists in the queue you know you can use
contains method just like how we have
used it with other collection classes
like list and dictionary we use it in a
similar fashion so for example queue
customers dot contains so this method is
going to return true or false so pass
the object that you want to check
whether that exists within the queue
let's say I want to check for the
existence of customer 1 object so if Q
customers that contains that customer
object let's go and print a message
saying
customer one exists else let's say we
want to print a message saying customer
one doesn't exist so thus not exist
alright so we do have customer one
object so what's going to happen it's
going to print customer one exists
message let's run this and look at that
if it doesn't exist you know it comes in
two else button it's going to print that
message all right so to add items to the
end of the queue use NQ method to remove
an item that's present at the beginning
of the queue
use DQ method a for each loop iterates
through the items in the queue but will
not remove them to check if an item
exists use contains method what is the
difference between DQ and peek methods
DQ method removes and returns the item
at the beginning of the queue whereas
peek returns the item at the beginning
of the queue without removing it that's
it for today thank you for listening
have a great day
video we'll discuss the generic queue
collection class queue is a generic
first-in first-out collection class
that's present in system door collection
store generic namespace that is the
order in which we add items to the queue
the same order will be used to retrieve
items from the queue the SKU collection
class is analogous to a queue at the ATM
machine to withdraw money the order in
which people QR will be the order in
which they will be able to get out of
the queue and withdraw money from the
ATM this queue collection class also
operates in a similar fashion the first
item to be added to the queue will be
the first item to be removed from the
queue let's understand the SKU
collection class with an example we'll
be using this customer class and this
demo and notice that this is
straightforward with three auto
implemented properties within our main
method we are creating five instances of
this customer class customer one through
customer five first of all let's go
ahead and create an instance of this
queue class so queue and what type of
queue do we want to create we want to
create a queue of customers the type
here is going to be customer and let's
give it a meaningful name let's call it
Q customers and just like how we can
specify an initial capacity of a list
and a dictionary we can also specify the
initial capacity of the queue using this
overloaded version of the constructor
but let's use the default constructor
that doesn't expect any parameters and
then to add items to a list we use add
method similarly to add items to a
dictionary we use add method but then to
add items to a queue we use NQ method so
let's go ahead and use that NQ method
and add an item to this queue so let's
add customer one object at the moment
there are no elements within this queue
so this customer one object will be the
first item within the queue let's now
add customer to object
so where will this customer to object we
added this customer to object will be
added at the end of the queue meaning
after customer one object so what is the
send queue method going to do look at
the intelligence it adds an object to
the end of the queue so these objects
will be queued one after another so
similarly let's add customer three
customer four and customer five all
right so these customer objects will be
n queued in that order one after another
because every time you invoke an NQ
method and then pass it an object that
object will be added at the end of the
queue now to retrieve an item from a
list we use you know its index the items
index within that list and similarly to
retrieve an item from a dictionary we
use the items key but then to retrieve
an item from a queue we use DQ method so
queue customers dot DQ and look at the
intelligence what is it returning back
it's returning a customer object back
because this Q is of is a collection of
type customer objects and then look at
what it is doing it is going to remove
and return the object at the beginning
of the queue okay so if you retrieve an
item from a dictionary by its key you
know it returns that item but then the
item will still be there in that
dictionary similarly if you retrieve an
item from the list using its index you
know it returns the item at that index
position but then the item is still
going to be present within the list but
then if you use this DQ method you know
the item that is present at the
beginning of the queue will be removed
from the queue and then returned okay so
let's store the item in a variable of
type customer and maybe let's call it c1
and let's say we want to print the
customers ID and name
so C 1 dot ID
and we want to print their name as well
so see one dot name so this DQ method is
going to remove and return the item so
after the first customer object is DQ'd
let's find out the total count of items
that are available still in the queue
and to find the total number of elements
that are available that are present in a
queue we can use the count property just
like how we have used it with lists and
dictionary collection classes so let's
say console.writeline total items in the
queue so queue dictionary queue
customers dot count and again we can
either use this count property I use
this link extension method we have seen
how to use this link extension method
with the list and dictionary so we would
use that in a same fashion with the
queue as well so let's use the count
property all right so let's go ahead and
run this now okay so look at that
if the output that we get but the
customer ID is 1 0 1 and name is mark
and if you remember you know this
customer 1 object has caught an ID of 1
0 1 and name is Mark so when we use this
DQ method since customer 1 object is the
first item that is present at the
beginning of the queue that's what will
be DQ'd ok now let's go ahead and DQ one
after another you know let's try and dig
you all these customer customers from
the queue and to speed things up I have
all the day types and code so let me
copy and paste that right here and this
code is very much similar to what we
have here so basically we are retrieving
customer to customer 3 customer 4 and
customer fired all the customers ok so
let's go ahead and run this and look at
this as vdq customers the count also
keeps reducing ok all right so what is
the purpose of DQ method it's going to
remove and return an item that is
present at the beginning of the queue
and to add elements to the queue we use
NQ method okay now is it possible to
loop through each item that is present
within the queue absolutely we can use
for each loop just like how we can use
you know the for each loop with other
collection classes like list and
dictionary in a similar fashion we can
also use it with our queue collection
class so for each customer let's call it
maybe see in customers queue customers
so let's go ahead and print their ID and
name and then the total items that are
left with in the queue so here the
reference variable is C so let's go
ahead and change that SC all right and
let's get rid of this piece of code so
basically at the moment within the queue
we have these five elements and then we
are using a for each loop to iterate
through the items within the queue okay
so let's go ahead and run that and look
at that you know it iterates through all
the customers within the queue and then
look at that the total count is still 5
as it is iterating through because the
for each loop will not remove the items
from the queue it simply iterates
through them and then in this case we
are printing their ID and name and then
the total items within the queue all
right now we know that the DQ method is
going to remove and return the item that
is present at the beginning of the queue
is it possible to return the item that
is present at the beginning of the queue
without removing it absolutely and for
that purpose we have a method called
peek so let's go ahead and use that
method look at that
when I say queue customer is dot peek
look at you know what the intercept
intelligence says this method returns
the object at the beginning of the queue
without removing it so let's get this
customer object out that is present at
the beginning of the queue and maybe
let's store in this variable C and then
let's go ahead and print
a ID and name okay so all we are doing
here is using the peek method to return
the item that is present at the
beginning of the queue we are printing
their ID and name and then we are also
printing the total count so let's go
ahead and run this okay
look at that we get the first item that
is present at the queue and look at the
total count it is still 5 so peak method
is going to return the item that is
present at the beginning of the queue
without removing it ok so that's the
basic difference you know DQ method is
going to remove and return it
whereas peak method is going to return
that without removing ok now what's
going to happen if I copy this piece of
code paste it here and look at that we
are calling peak method again again
let's call this reference variable C 2
okay now so here it's going to return
the object that is present at the
beginning of the queue which is customer
1 if I invoke a peak method again will
it return customer 1 object or customer
2 object it will return still customer 1
object because that is present at the
beginning of the queue and it's not
removed so no matter how many times you
call this peak method you are still
going to get the same object which is
customer 1 because that is still present
at the beginning of the queue alright
now how to check if a specific item
exists in the queue you know you can use
contains method just like how we have
used it with other collection classes
like list and dictionary we use it in a
similar fashion so for example queue
customers dot contains so this method is
going to return true or false so pass
the object that you want to check
whether that exists within the queue
let's say I want to check for the
existence of customer 1 object so if Q
customers that contains that customer
object let's go and print a message
saying
customer one exists else let's say we
want to print a message saying customer
one doesn't exist so thus not exist
alright so we do have customer one
object so what's going to happen it's
going to print customer one exists
message let's run this and look at that
if it doesn't exist you know it comes in
two else button it's going to print that
message all right so to add items to the
end of the queue use NQ method to remove
an item that's present at the beginning
of the queue
use DQ method a for each loop iterates
through the items in the queue but will
not remove them to check if an item
exists use contains method what is the
difference between DQ and peek methods
DQ method removes and returns the item
at the beginning of the queue whereas
peek returns the item at the beginning
of the queue without removing it that's
it for today thank you for listening
have a great day
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Apr 29, 2026 Last updated
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