🔥Kotlin Tutorial for Beginners Kotlin Android Tutorial Kotlin for Android Simplilearn

hey everyone welcome back to another
video session by simply learn
in this video on kotlin tutorial we will
be learning about kotlin language and
all the basic concepts that one must
know to understand this language
so let's go ahead and understand what we
will be covering today
so we will start with introduction to
kotlin language then we will understand
the variables in kotlin after that the
conditional statements like if else and
when
then we will cover array loops null
safety and ranges in kotlin and at last
we will learn about kotlin functions
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so let's start with introduction to
kotlin language
kotlin is a journal purpose statically
typed programming language developed and
released by jetbrains in 2016.
in 2011
jetbrains revealed the kotlin project
which is a new language for jvm
and later in february 2016 its first
version kotlin 1.0 was released
this language is concise and more
expressive than java
it is fully interoperable with java and
it is also said that kotlin language is
made by extracting all the good parts of
different programming languages like
scala javascript java c-sharp etc
google also announced kotlin as the
first class language for android
development
so it is now an official language for
the development of android and is being
opted by many organizations across the
globe
now let's move on to our next topic
which is variables in kotlin
there are two types of variables in
kotlin which are
where and well
first where
the var variables are mutable which
means their value can be reassigned
then there is val the valve variables
are immutable which means their value
cannot be reassigned or changed or
modified
as you can see in the example where is
the type of the variable name and the
value raj is assigned to it after that
the value is reassigned as said
so after printing it will display set
because where is mutable type and its
value can be reassigned
on the other hand
val is the variable whose value cannot
be reassigned
which means it is immutable
as we can see in the example on printing
the value of the name variable
it is showing an error because we tried
to change or reassign the value from raj
to sid
and because it is a val type variable
the value is not going to change
kotlin
is smart enough to understand which is
string and which is an integer
so it is not necessary to specify the
type
like in this example
name is the string and roll number is
the integer
but we haven't specified their type
and still there is no error
however it is possible to specify the
type if you want
now coming to next topic which is string
templates
a string can be defined as a collection
of characters enclosed in double quotes
the string templates allows us to
include the expressions variable
references inside the string
the references in a string start with
the dollar sign
to print the string
we need to add the dollar sign before
the string name
we can easily add the variables in the
string instead of concatenating them
for example here name one and name two
are two strings and we can include them
together
within the same sentence while printing
like both
dollar sign name one and dollar sign
name to our best friends
it will display the value of string
within the sentence
we can also print the expression like we
did while printing the second sentence
dot to upper case
dot upper case is an expression and in
kotlin expressions start with a dollar
sign
and are enclosed in the curly brackets
as you can see
so as we have understood about the
string templates
let's move on to if-else and when
statements
if is used with a condition
if that condition is true
then the block of code executes and if
the condition is not true or false then
the else block executes
now in quarterly language the if-else
statements can also be used as
expressions that means they can return a
value
while using if else as an expression it
is mandatory to use the else branch
here in the example we can see if a is
greater than b is the expression and the
value of that expression is assigned to
the variable named great
now which so ever is greater among them
that will be assigned to it and is then
printed
now
coming to when statements
when statements in kotlin is similar to
switch statement in java
when statement is used to select one
code block from the multiple code blocks
based on a conditional expression
the code block which satisfy the
condition is executed
for example as you can see the value 4
is assigned to the variable tab
now
which server value matches with the
value of tab
that particular code block will execute
in this case there are no code blocks
but single line branches
the branch value that matches with the
value of tap that particular branch will
execute
like wrap will execute which is then
stored in the order variable
which is then printed
now
let's move on to arrays in kotlin
arrays are generally used to store
multiple values in contiguous memory
location in a single variable
in kotlin language to create an array
you have to use the address of function
and then
write the elements inside the bracket
for example here name is the array name
and sid robbie max john
are the elements of the array
in order to print the elements of the
array you can use loops for example here
we are using for loop
in this for loop n is the variable
names is the array name
and one by one it will print every
element of the array
now
as we have understood about arrays
now let's understand about loops
loops are used to iterate through the
different parts of program
for example arrays
ranges several times
it is a set of instructions which keeps
on repeating until a certain condition
is met it is generally used while
working with arrays
in kotlin language the for loop is bit
different to that in java
in this for loop we use a variable in
operator and the array name to display
the elements of the array
for example as you can see in the
example
there is an
array with elements 4 2 5 12 7 and using
the for loop we are displaying the
elements of the array inside the for
loop
here n is the variable n is the operator
and numbers is the array name
loops are also used to iterate through
the ranges
which we will discuss
later now
let's understand why loop and do while
loop
both these loops are similar to the
loops in java
the function of the while loop
is it checks the condition and executes
through the block of code as long as the
specified condition is true
and the do while loop executes the do
block once before checking if the
condition is true
which means the loop will execute at
least once even if the condition is not
true
so as we have understood about loops in
kotlin so now let's move on to our next
topic which is null safety
so null safety is a feature in kotlin
language that solves the problem of null
pointer exception
if you have worked on other languages
including java then you must have an
idea of null pointer exception
in cotton language you can easily create
null type variable
to create a null type variable or string
which can hold a null value we can
simply define them by putting the
question mark at the end
as you can see in the example name is
the variable name and string is the type
and after string there is a question
mark which means that this variable is
of null type
by default all the variables are not
null in kotlin
but you can create one by putting a
question mark with them
now moving on to the next topic which is
ranges
now ranges can be defined as an interval
from start to end
expressions are created with double dot
operator and an in operator here in the
example 0 is the starting point and 7 is
the ending point in between them there
is operator double dot operator which
means that the loop will iterate from 0
to 7.
similarly we can also print the range
with gaps like in the example i in 0 to
10 step 2
means that it will print from 0 to 10
the gap of 2 digits like 0 2 4 6 8 10
range can also be used in decrement
manner for example
i in 7 down to 2
means the loop will iterate from 7 to 2
in a decreasing order
now
let's move on to the next topic which is
kotlin functions
functions are also known as methods
they are the block of code which runs
whenever it is invoked
in kotlin language functions are defined
with the fun keyword after that the name
of the function and parentheses
are written
if the parenthesis are empty it means
function doesn't accept any arguments
in function with parameters the
parameters are specified inside the
parenthesis
the type of parameter is specified after
the name of the parameter
so we can see in the example fun is the
name of the function
num1 num2 are the parameters name
int is the type of the parameters
then after that the colon there is
another int data type
which is the return type that means it
is the data type of the value which is
returned
so these were some important topics of
cotton language
now let's go to the code editor
and do some practical implementations
so this is our intellij idea here we
will do some examples of cotton language
so let's go ahead
first of all
we'll create the kotlin file
so let's name it as example one
so first we'll do an example of string
template
in which we'll have a look
that how to create those strings and how
can we use some expressions with them
so let's start
so fun is the keyword for function
now main function
now inside this main function
we'll write
val
this is immutable as we know
code is the name of the variable
now let's say
code is
cipher
in kotlin language you don't need to put
the semicolon in the end as it is not
necessary you can do it but it is not
necessary to do that
all right now
after that let's say you want to print
this
we'll write
the code is
dollar sign
code so this is how we can
print this string
and
let's see that if it works or not first
of all we'll have to save it
so we'll do save all
and now we'll go to run
now here we will
run run and select example one
all right
as you can see the code is cipher it is
getting printed
now let's say
we want to use some expression with it
right
the code is let's say we want to write
the code in capital letters all right
the code is
dollar sign and then the curly brackets
and inside the curly brackets we'll
write code
dot
upper case
yes
uppercase
now with brackets
now after that
you want to put the semicolon it is your
choice otherwise it is not required
so now let's save it again
evolve and now
let's try to run it
as you can see the code is cipher the
first one the code is
in capital letters cipher
so this is how we can do it and we can
also merge
the strings we don't need to concatenate
them
so we can do like this the code is this
and
right
now let's try to run it again
so here what we are doing is we are
merging the uppercase and lowercase
here we can see the code is cipher and
cipher
so this is how we can
concatenate both the strings easily so
this is one of the example of string
template
now let's do another example of
if else statements as expressions
let's go ahead
right
now we'll create
main class fund main
and inside this main function
first of all we'll create two variables
that is
marks one
of well type
and let's assign it value 87
then another variable marks two
and we'll assign it as let's say 82
here we are using if else as expressions
so what we'll do is
we'll make a variable result and we'll
store the value of if or else in that
particular result and then we'll display
that particular variable
and let's say that variable is
result
here we will use if else as expressions
so
val result equals
if
max 1
is greater than
max
2
then
in the bracket
right
marks one
equals this is for the printing purpose
dollar sign
marks one
is the greater
among both
let's write
is greater
than
max2
variable marks
two
all right
now similarly we'll do four else as well
write else
now similarly
we'll write
max2
equals
max2 variable
is the
is greater
than
marks one
all right so after that we'll print the
variable result because the result is
getting stored in this variable result
so whichever is greater will get stored
over here and then we will print this
variable
println
and we'll write
result
all right
now it's done and i think we have
to run this one
save it and let's try to run
example 2
hope it works
as you can see
marks 187 is greater than marks 82
as
max 1 is 87 and max 2 is 82
so marks one is greater so that is why
if block is getting printed
now
let's do an example of when statement
let's create a new file
go to new
this
kotlin file
now let's name it example
three
all right so this is example three
now let's start with the one example
function main
inside this we'll create a variable
named coupon so let's say the variable
is where
coupon and let's assign it a value
5
all right now
the when statement works as switch
statements
it is used to select one code block or
one code branch out of many code blocks
or code branches based on the
conditional expression
which so ever code branch matches with
the condition that particular code
branch will execute
all right so
let's start with it
we'll use when keyword
and let's say
open is the
name of the variable and the value of
coupon is 5 as you can see as we have
already declared that
now
inside when
the first branch would be
so this is how you can create a first
branch
and if there are multiple lines then you
have to use the brackets
all right so here we will print
here is your
coffee
all right so first message is this
the second message would be like
forgot to enter t
yeah
so the second message let's say here is
your t we will write
over here is
your t
so in the third branch
we'll write
here is your green tea
the fourth branch you will write
here is your juice
and in the fifth line or the fifth
branch
we will write here is your water
so
this is how we can create this we can
also create a default
value that we have to use the else
statement
and write else
right invalid
input
all right so this is how we are doing it
and so the value of coupon is 5
and
whichever values among these like one
two three four five five obviously will
match it
that particular
statement or
line will be printed
let's save this one
and let's try to run it
so there's an error as you can see so
for that
we have to use the arrow operator
instead of this bracket
so let's do that
so now if any value other than these
five values is there in this variable
then this
default message will be printed that is
invalid input
so now let's save it
again
and now
run it
as you can see here is your water as the
value was five
let's say the value is
six
it must show
the invalid and input as there is there
are only five values
so now let's try to run this and let's
check
if it is working fine or not
as you can see invalid input
as we have entered six over here
which is not in this one two three four
five so that is why it is printing
invalid input
now let's do an example of array
let's create a new file
portland file
now let's name it example
4
all right
now the main function
right now inside this function first of
all we will create an array
so how we will do that
well
let's say the name of the function is
arr1
equals
array
off
as we have discussed already array of
now the number of elements
like 2
4
6
8
12.
these are the elements of array1 now
similarly we will create an array2
right
array
array off
of the elements
1
3
5 7
9 11.
all right now
now here we will use
a set function
so if we want to set a particular
element at a particular position then
we'll use set and if we want to display
a particular element of the array then
we'll use get so first of all we'll
understand set
so
array1 dot
set
so first here we will write the position
let's say 1 is the position and at one
position we want to set five as an
element
so this is the syntax for it
and let's say for array two
array array2.set
now here we want to set
at zeroth position
and we want to set
two element
so first is the position and second is
the element
that we want to set at that position
all right
now
[Music]
now we'll see the get
function
so
get is used to display the particular
element of an array
so let's say array1 dot get
let's say i want to print the fifth
element
that is 14th in array1 case
so i'll do this
similarly for array two
and in array two case i want to print
this
fourth element
that is nine
now
after that we'll use println
so that the result come out vertically
all right now if we want to print each
and every element of an array so this is
how
we can do it
for
element
in
arr1 here element is the variable
array1 is the name of the array
and one by one it will print
all the elements so here we will write
element
just for the space
now again we'll use for loop
here we will display the elements of
array 2.
yeah it's done
let's save it now
and now let's run it
as we can see
14 n9 so as we know here we have set
five at one position at first position
so zero one so in at place of four there
is five now
and here at zeroth position that is at
one position there is two
so first of all here we have
printed this get five
so at
array one position at fifth position
zero one two three four five there is
fourteen so that is why it is preventing
14.
in array 2 at 4th position there is 9 so
here it is printing 9
after that
here we are printing all the elements of
the array so as we can see at the first
position
we have set 5 instead of 4
here we are doing that so that is why
here we can see 2 5 not 4 then 6 8 12
14.
similarly as you can see at 0th position
in array 2 that is here we have set 2
so we can see
instead of 1 there is 2 3 5 7 9 and then
11
so this is how we can
add some elements at a particular
position and print those elements and
print the array as well
so now let's do another example
right so we'll write function main
now inside this we will create an array
well arr1
now in kotlin
you can create an array having the
integer elements and character elements
or string elements as well in a same
array
so i'll show you that
array off
so first we'll write down the integer
elements let's say 2 4
6
and then
the string
elements let's say
8
and then 10
so this is our array
within the same array there are integer
elements and string elements
all right
now using for loop
we'll try to print this
element in
array one dot
here dot indices means if we want to the
print the index of each of these
elements
let's say if we just want to print the
elements so we'll not use this
we'll simply
print ln
and then we'll do is
array 1
this is just for printing purpose
element
then
all right
so now let's save it
let's run it
as you can see
2 4 6 8 10 it is printing without any
error so we can easily do that
in kotlin
and these are the
indexes for the index if we want to
print the index of these elements we'll
do is dot
indices
now let's save it again
and run it
as you can see array of one with zero
index zero one two three four
the index is correct but the elements
are not
so i think this yeah we forgot to write
array off
in the bracket
now
let's save it again
now let's again try to run this
a01
yeah
now again let's try to run this
all right as you can see
array with index numbers will print 2 4
6
8 10.
so
not only the integer elements are
getting printed but also the string
elements are also getting printed along
with the index number
because of this dot indices
we are also able
to print the index of array elements
so these were some examples of kotlin
language you can try some more examples
on it the more you'll practice the more
you'll get to know about this language
all right with that we have come to the
end of this video
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