#10.1 Kotlin Android Tutorials Collections Introduction and ARRAYS in Kotlin

hi Lisa stirrings at the heart once
again welcome to the next module of this
course of Cortland programming now in
this module II will talk about
collections in Cortland so first of all
what are the topics that we will cover
in this module so firstly I will show
you what are collections by simply using
the examples of arrays in Cortland now
the air is in Cortland are actually
mutable in nature but has fixed size now
if you are from Java background then you
must be knowing what this array stands
for it is simply the collection of
elements that is integer strings and so
on such as array of string array of
integer array of float and so on so we
will check out what is the array and
what does this mutable stands for and
why do we say that array has fixed size
now proceeding forward we will check out
the actual collections in Cortland such
as the immutable collections and also
the mutable collections right now if you
notice the two sections here the
immutable collection and mutable
collection you can notice immutable
collection are actually read-only that
is once we define the collection that is
the array or list or map or set we can
only read data from that collection but
the mutable collection supports both
read and write operation that is once we
define our collection such as the list
or math or sets we can read and write
both that is we can modify the list or
the collection in future as well so
similarly the array is actually mutable
in nature that is we can modify our
array in future as well so in this video
just for the introduction I will show
you what is an array and how can we
define the array in Kotlin so if you
understand the concept of array in this
video then from the next video onwards
you won't face any difficulty to
understand the list map and sets both
immutable and mutable so let's check out
the array inside the IntelliJ IDE
so here inside the IntelliJ IDE just to
define the array the syntax is like this
so where or well let us define the name
as my array as of now equal to let's say
array now it expects a template that is
the type of array that you want to
create so as of now I want to create the
integer array the array that will hold
only the integer value so as a parameter
by defining the array object that is my
array you have to define the size of the
array that is the number of elements
that this array can contain or the
integer values that it can contain so as
of now I will simply give five now
proceeding forward give it a space and
here it expects the second parameter as
a lambda value now we already know what
this the lambda in case of Kotlin stands
for so inside the lambda that is in
between the parentheses that is the
curly braces you have to define the
initial value of all the elements of the
array so here let us initialize it to
zero right so we have simply defined the
array of integers that is my array that
can only contain 5 elements and the
initial value of all the elements is 0
now if you look at the representation of
the array or typical array you will find
this right so here I have 5 elements so
all the 5 elements is actually
represented with the help of a
particular index so this is the index
such as 0 1 2 3 & 4 now notice we have 5
elements but the index starts from 0 and
ends in 4 that is 5 minus 1 is 4 right
if I put here 6 then the index will move
ahead such as 5 and value will again be
0 now these are the elements initial
value that we are defining it here so
all the elements initially has the value
of 0 now if I put here let's say minus 1
so instead of 0 we will have minus 1
minus 1 and so on
all the values will change from zero to
minus one so as of now let us keep it
zero only right that was just to show
you now now proceeding forward as said
the Aries are actually mutable in nature
but has fixed size so once we have
defined that the array should only
contain the five elements so it will
only have the five elements right we
cannot make it six in future right and
it is mutable in nature that is we can
modify the values present inside the
array such as if you want you can change
the element at the index of zero to
let's say thirty two so now when the
code will be executed this 0th index
that is that this index will now contain
32 instead of zero so here zero will now
become 32 right now if I change let's
say my array index of let's say 3 I want
to change the third index element to
let's say 54 so here instead of 0 I will
get 54 as the integer value right so
this shows that the errors are actually
immutable in nature that is once defined
you can change the values right now if
you want to print the values so for that
you can simply use print line let's say
my array and simply use the index now to
define the index you simply need to use
the square brackets square bracket open
and close now inside this you will
simply use let's say I want to print the
third element or the fourth element so
for that you have to use the index of 3
so let us now run the code so in the
output console we get 54 as the output
now if you want to print all the
elements present inside the array that
is right from 32 till 0 so for that we
need to use the for each loop such as
for loop define element in operator
followed by my array now the concept of
for loop we already saw in the previous
module right so let us define let us use
print line statement
or instead of this simply use element so
this will simply print all the elements
present inside the my array and here we
get all the output 3200 54 and 0 now
make a note here that the element
present at 1 & 2 & 4 we have not yet
initialized that is it is by default 0
that we have defined here so if you want
you can also change modify the value by
providing the index let's say index at 1
equal to 10 or 11 like this let us now
run the code and here we get 11 here
right now if I suppose use the index of
let's say my array for the index let's
say 9 or 8 equal to let's say 23 so
since we know that the size of the array
is only 5 so from where we are getting
the 8 index so if I run the code right
now it will simply throw an error that
array index out of bounds exception
right as expected
array index out of bounds exception
because our array does not contain the
8th or 9th element right so there is no
possibility of having the index of 8 so
that is why it has simply thrown the
error and that is why we say that we
cannot add more elements as mentioned
here in future so that is why please
make a note please remove this code and
now we are simply printing element
inside the array and simply printing the
element suppose if you want to print all
the elements with the help of the index
so for that what you can do is simply
use the for loop provide the index
variable in my array or the range 0 dot
dot let's say 4 so index will now vary
from 0 1 2 3 & 4 now to be more specific
so here we have 0 1 2 3 & 4 like this
right now to be more specific instead of
4 you can simply use my array dot size
minus 1 that is my array dot size will
simply return 5 right so minus 1 will
now read
four so this will now become finally
four like this
so it is a more generalized form and
then simply print the my array of the
index so the index is simply vary from
zero one two three and four and it will
simply print out all the elements
present inside the array so here let us
use red line or the newline character
and now run the code so in the output
console we get 32 till zero and then
again 32 till zero so in both the ways
the codes are working perfectly fine so
this is the way to print all the
elements inside the collection so in the
upcoming videos we will use these two
loops again to print out all the
elements present inside the collection
now at the end of this video I would
again like to highlight this point that
this array has a fixed size so this is
actually the problem for us suppose we
want to add elements in future but you
cannot do it so for that we will check
out the array list in court Lane in the
next video
so please make sure you check out my
next video this is shrinks without
signing off and thanks for watching and
have a good day