#11.2 Kotlin Tutorials: PREDICATES: all; any; count; find. Using Lambdas in Collections PART-2 Video Lecture | Kotlin Tutorial for Beginners: Learn Kotlin in easy language - Back-End Programming

hi registering to the Hart's once again
in the previous video we talked about
the filter and map methods now in this
video let us talk about predicates in
case of Kotlin now the predicates in
simple words it is just an condition
that simply returns a boolean value of
true and false so what are predicates
functions so here we have all any count
and find so the all method simply ask
the question do all elements satisfy the
predicate or the condition so it will
simply return either true or false that
is a boolean value
now here down the side I have any so
this any method simply asked a simple
question do any of the elements present
inside the list satisfy the condition or
the predicate and it is simply again
return true or false now down the side I
have a count method that simply returns
the total number of elements that
satisfy the condition or the predicate
and at last I have a find method that
simply returns the first element that
satisfy the predicate so from the list
it will simply check out the first
element from the starting that simply
satisfy the condition and simply return
it so let's check out the code in action
inside the IntelliJ IDE so here again I
have the list of numbers 2 3 4 6 23 and
90 and so on now let us start using the
functions of the predicate such as my
numbers dot all let us start with all
method this all method simply expects a
lambda function right so here I will
simply define the lambda function that
will be actually a condition so here I
will simply use num going into num
greater than 10 so find all the numbers
that satisfy this condition right it
simply means this only now since here we
have only one parameter num so it can be
replaced by it it greater than 10 now
this all method simply returns a boolean
value so I will simply use Val
check when equal to my numbers dot all
so this statement simply asked that are
all the elements greater than 10 if yes
then simply returns true if not then
simply returns false right so in our
case it was simply return false because
all the numbers are not greater than 10
now if you notice here all is a function
that takes the first parameter as the
lambda expression so you can also use
the function type here as well so as a
first parameter I am simply passing a
lambda now the purpose why I am using a
function here I will shortly let you
know now here let us print the
checkpoint so as expected we get false
in the output console now let us use my
numbers dot any so this any method
simply now expects a predicate so here
inside the function I will simply pass
the lambda expression about let's say
num going into num greater than 10 now
here again let us replace it by it so
this statement simply asked the question
does any of these elements satisfy the
condition or the predicate so here we
have few of the elements such as 23 and
90 that simply satisfy this predicate
right so it will simply return true so
let us use a boolean variable valve
check 2 equal to num now this check 2 is
actually of the type of boolean so I
guess no doubt in this very simple and
then simply print out the check to so in
the output we get through here as well
and now proceeding forward let us now
check out the count so my numbers dot
count so here again I will simply pass
the lambda expression let's say I T
greater than 10 so this statement will
simply return the number of elements
that satisfy the predicate so it will
simply return the integer value let's
say well total count equal to my numbers
now this count will be of
type of integer right and now let us
print out the value of total count so
here we have two so there are only two
numbers that is twenty three and ninety
that satisfy our condition or the
predicate now at the end I have let's
say my numbers dot find now this again
expects a lambda as a first parameter so
I will simply use I T greater than ten
the condition will be same and here it
will simply return the first number that
matches the predicate so it will simply
start counting from two and look further
and look for the integer variable that
simply matches the condition that is the
predicate so as soon as it reaches 23
the condition becomes true so 23
actually satisfy this condition i T
greater than ten so it will be then
stored inside the value of let's say num
equal to my numbers right and now let us
print it out print Ln num and now let us
run the code so here in the output we
have 23 and we did not get 90 in the
output console because 23 is the first
element starting from the list that
satisfy the condition of let's say I T
greater than 10 now if we check out the
documentation of the find you will find
that it simply returns the first element
matching the given condition or the
predicate or null if no such element was
found so this simply shows that this
number is of the type of nullable
integer right so it can also contain the
null value and now if you notice here
that in each of the function we have the
repetition of the predicate ID greater
than 10 by T greater than 10 and so on
here as well so as said in the previous
videos that we can store the lambda
function as a variable so here what I
will do is I will simply define let us
say my lambda let's see my predicate to
be more specific
equal to let's say I T greater than 10
now the compiler don't understand what
does IIT stands for here because here
the IIT is standing in context of my
numbers so all the numbers here are
being represented as I T in context of
my numbers which is the list of numbers
but here we don't have any list present
here so the compiler does not understand
what does this I T stands for so for
that you have to simply use the num
variable going into num greater than 10
now again we have some error what is the
type of this number variable so you need
to specify it here as well int so this
completes our lambda function now now
instead of using the it greater than 10
everywhere you can simply replace it by
my predicate here and again my predicate
here and here as well let us replace it
by the function my predicate remove it
from here
and down the side here as well let us
put the brackets inside which my
predicate and now let us run the code so
here as well we are getting the same
output in the output console so always
remember this about all any count and
find now there are lots of other methods
as well that you can find here such as
last last then and so on you can get all
these methods down the side so as of now
I just showed you all the important
methods so this video was just to show
you what are predicates in case of
Kotlin so the predicate in short are
just a condition that I have declared
with the help of a lambda function so
always remember the predicates are just
a condition that returns either true or
false so this was all about this video
thanks for watching this ranks without
signing off thank you and have a good
day