#10.2 Kotlin Android Tutorial LIST and ARRAYLIST Mutable and Immutable

hi reassuring Siddarth once again
welcome to the next video of this module
of collections now in this module we
will check out the immutable collection
and mutable collection so first of all
in this video we will check out what
does list stands for so in case of lists
we have the immutable list and also we
have mutable list so we will check out
one by one what does the immutable and
mutable is stands for and what are these
functions such as list of ArrayList
ArrayList of and mutable list of stands
for so let's check out one by one and
slowly inside the IntelliJ IDE so in the
previous video we checked out what our
arrays in case of Kotlin now the demerit
of array is that it has a fixed size
defined so we cannot change it later so
here what I will do is I will simply
modify my code so here I will simply
delete all these code from here now to
define a list we need to simply use the
VAD or Val keyword and then simply use
list equal to use the list of keyword
right and now here as a template let us
define string and now as a value you can
simply define the content of the list
such as Yogi Manmohan and at last
watch pay so here I have simply defined
the immutable list by using the keyword
of list of now this is the type of list
that we are having so this list variable
will only contain the string values or
you can say the array of string right so
here as a value I have Yogi Manmohan and
watch pay we are having three string
values right now as per this slide here
this list of keyword only creates the
immutable list right so let me add a
comment line here that is this list is
actually immutable in nature and also it
has fixed size and most importantly we
can only read from this list that is
later on we cannot modify the list or we
cannot write anything extra to
list that is once the content of the
list has been defined it cannot be
changed what I am trying to say is you
cannot use such as lists of let's say
index to equal to let's say something
right
ABCD right you cannot do it because the
Cortlandt does not allow you to do it
because the list is actually immutable
in nature you cannot modify it later you
can only perform the read operation now
what do I mean by the read operation is
you can only print out the values
present inside the list using the loops
that we saw in the previous video right
and one more thing is common for this
list compared to the arrays is that the
lists also have the sequential index
that is this you he has the index of
when this element has the index of sorry
this yogi has the index of zero manmohan
has the index of one and this watch bay
has the index of two and so on it will
continue if we have further elements
right so as of now let us remove the
elements of integer and in case you want
to enter the int value so you can simply
define the enter type and simply replace
all these value by integer values now
same applies to the float or let's say
boolean or let's say string right and
now let us print all these values such
as I place my array by list and then
here let us replace my array by list dot
size minus one right and here again use
list of the index now apart from this
list index of index you can simply use
list dot get function and simply pass
the index so this loop is actually using
the index of the element objects to
print out the values right and instead
of lists of index you can simply use you
can also use list dot get index so as of
now let us run the code and let's see
what happens so here we get yogi
manmohan and watch pay and again we get
yogi manmohan and watch pay right so our
codes are
working perfectly fine now suppose later
on you want to add the fourth element
that is here you want to add one more
element so for that this list off is
actually immutable in nature so the
solution for this is that you have to
use the mutable list so here from the
slide you can check out the mutable list
we have the error list option ArrayList
of option mutable list of option so
either of these three you can use as per
your choice so as of now let us replace
this list off by let us say mutable list
off right so this now makes our list
immutable in nature so let me modify the
comment line so this new table list off
is actually mutable in nature and it has
no fixed size you can add as many
elements as you want to and also you can
perform the add or remove operations
such as read or write operations as
discussed because it is immutable in
nature right so inside the list what you
can do is you can simply use you can
simply add more elements such as list
dot let's say add so here let me add
yogi so if I add yogi here then you can
remove yogi from here right similarly
you can add more elements after the
declaration of the mutable list so since
we have added the manmohan and watch
page here so let us remove these
elements from here so it can be blanked
so this initialization of the list
variable can be blanked right now after
this
suppose if I run the code right now it
is simply going to print out these three
elements in the output console as
expected yogi manmohan in watch Bay now
later on suppose you want to perform
more operation on this mutable list so
for that what you will do is you can
simply use as many methods as you want
to and these methods are actually
predefined such as add method replace
all method remove the element at a
specific index set the element at a
specific index get the size of the list
and get a specific element at a
particular index and so on right so as
of now what I will do I will simply
remove the element of let's say my
movement right and instead of manmohan
that is present at the index of let's
say 1 so here I have simply defined the
index of the element this manmohan is
present at the index of when so instead
of manmohan I want to add Moody so for
that what I will do list dot add provide
the index of let's say when add the
index of 1 simply add Moody instead of
manmohan let us now run the code and
let's see if it happens or not so here
in the output console we have yogi moody
and wash face so the manmohan has been
replaced by moody right now instead of
this using the remove and add method
that is predefined we can also use lists
at the index of when equal to let's say
moody right so this list at the index of
when simply replace whatever is present
at the index often by Moody so let us
now run the code so here we get yogi
moody and wash Bay again so instead of
using these two lines of code we have
only one line of code that performs the
same operation as done by these two
lines of code altogether and now at the
end instead of mutable list we can also
have let's say array list of strings and
also instead of this you can also use
array lists now to be specific in all
the cases we are actually using the
mutable array list such as here we have
the ArrayList of string here we have
ArrayList of method that simply returns
the ArrayList right and here again
mutable list of actually returns the
ArrayList object so if you define the
type let us say alt-enter specify type
explicitly you will find the mutable
list which is the more general form and
here again for
this alt-enter you will find ArrayList
of string and here again specify type
explicitly you will find ArrayList of
string now this mutable list is actually
implemented by the ArrayList of string
so all these methods such as mutable
list of ArrayList of an ArrayList
are all same so you can use either of
these three just for the sake of your
more information I just showed you the
explicit declaration
so let us revert it back and here let me
comment these two lines of code and here
ArrayList of string is again going to
work perfectly fine let us run the code
and let's see if we are getting the same
output or not yes yogi move the and
watch by again in the output console so
remember at the end we have list of
method that simply returns the immutable
list and here we have the mutable list
such as ArrayList
ArrayList of and mutable list stop you
can use either of these three in your
code so in the next two videos we will
check out math and sets in Kotlin so
this shrinks without signing off thanks
for watching and have a good day thank
you