21
Aug

Passing, Returning Arrays To / from Methods in Java Programming Video Tutorial


This is Anil from Learning Lad education and
welcome to another tutorial on Java programming language. In the previous tutorials we have learnt about
the methods in Java and also I have taught you guys how exactly we can pass parameters
to the methods and here in this tutorial we are gonna learn how exactly we can pass an
array to a method and also how exactly we can return an array from a method. So just for the demonstration purpose in this
tutorial what we are gonna do is, inside my main method i’m gonna create an Array. so I just gonna create an integer array and
lemme call it as marks and inside this array i’m gonna store some integer values and lets
say 22 66 33 99 88 77. now what we are gonna do is we are gonna create
a method and we are gonna pass this marks array as the argument to that method. so after this Main method inside my tutorial
class, i’m gonna create a method. so first we need to write the modifiers. So its gonna be Public Static and after this
modifier part, we need to write the return type. Here i’m gonna assume that my method is gonna
return void type. It means no return values. so I just gonna use void, and then we are
gonna write the method name. The method that I’m gonna create here is gonna
take an integer array as a parameter and its gonna display the elements of that array. so I just gonna call this method as display,
and then a pair of parenthesis and then a pair of curly braces. now between these parentheses, we need to specify
the parameters taken by this display Method. here our method is gonna take an integer array. so I have to declare an integer array here. so I just gonna use the data type as int, then
a pair of square brackets and then I just need to give a name for the integer array. so I just gonna call it as input. now our display mythos is not gonna return
any value and its gonna take an integer array as a parameter. so inside this display method, we are gonna
display the elements of this input array. so I’m gonna use a for loop. so its gonna be for and we are gonna need
a loop counter variable and i’m gonna declare that right here and i’m gonna initialise that
one to 0 and then we need to write the condition part. So its gonna ne counter less than, we need
to loop through all the elements of this input array. so we can get this length of the input array
by using the length property. so Its gonna be input, the array name dot
operator and then the length and then we are gonna have the semicolon and we need to increment
the value of the counter variable. And after that we are just gonna use the print
line Method. So its gonna be system dot out dot printline and here we are gonna refer the input array and we are gonna refer the the element
position by using the counter variables value. so this display method now, its gonna take
an array as a parameter an integer array as a parameter and its gonna displays the elements
of that integer array. So now we are gonna call this display Method
from our main Method. so here I’m gonna write display, the method
name and then I have to pass this marks array. so I just gonna write marks here as the argument
and i’m gonna save this program and i’m gonna run this. And now you guys can see here, the elements
of that array 22 66 33 99 88 and 77, are successfully passed to this display method and we have
successfully printed the element of the passed array. so this is how you guys can pass a single
dimensional array to a method. The next thing that I want you guys to teach
you is,how exactly we can return an array from a method. So here in my tutorials class, i’m gonna define
another method. which is going to take an integer array as
a parameter and also its gonna return an integer array. The method that i’m gonna create is gonna
take an integer array and its gonna create another array with reversed element of the
passes array and its gonna return that reversed array. so we are gonna write the modifier part and
its gonna be public and then we are gonna have the static keyword and after that we
need to write the return type. here our method is gonna return an integer
array. all of you know that if you want to return
an integer value from a method, you guys need to use the keyword int.
here in this case we are returning an integer array. so we are gonna use the square brackets to
specify that we are talking about the arrays here.
and then we just need to give a name for our Method and here our method is gonna reverse
the array element. so I just gonna say reverse array. and then
we need to have a pair of parenthesis and then a pair of curly braces. now as a parameter to this reverse array,
we are gonna pass an integer array. so All of you know how you can do that. just now I have taught you about that. So its gonna be int and I’m gonna call this
array as input. All right. now what we are gonna do is we are gonna can
create another array inside this reverse array method. because we don’t want to reverse the element
in this input array. we want to reverse the elements and then we
want to store it in another array, and we want to return that array. so what we gonna do is we can create an integer
array. so our array is gonna be of type integers. So i’m gonna declare it. So its gonna be here int and then the other
name and then i’m gonna say reverse and and then we are gonna write new you know the new
keyword to create an Array and then we are gonna have the data type which is gonna be
int and now here between the square brackets, we need to specify the length for this reverse
array. now this reverse array is gonna contain the
element of this input array in reverse order. So the length of this reverse array is gonna
be equal to the length of this input array and I all of you know that we can get the
length of this input array by using the length property. so I’m gonna write input here then the array
name and then i’m gonna use the dot operator and then I’m gonna use the length property
and the next thing that we are gonna do is we are gonna loop through all the elements
of this input array and we are gonna store that and reverse order. For that purpose i’m gonna use a for loop
and inside this for loop we are gonna use two variable. one for the input array and one for the reverse
array. so I’m gonna create a variable called i and
this variable is gonna be for the input array and that’s why I’m gonna initialize that one
to a value of zero. And then we are gonna need another variable
for this reverse array and that variable is also going to be of type integers and I’m
gonna call it as j. here we are gonna initialise this j variable
with one less than the length of this input array because in an array the last element
will be stored at the position One Less than the length of that array. so here what we are gonna do is, first we
are gonna take the first element from the input array and we are gonna store that in
last element of the reverse array. so here I’m gonna use reverse dot length minus
one. so our i is going to be equal to zero which
begin with the first location of the input array and this j is gonna contain a value
which will indicate the last position of this riverse array. and then we need to write a
condition. we want to run this loop until we loop through
all the elements. so we are gonna use the condition as i less
than input dot length and then we need to write the updation part. here we want to increment the value of i. So its gonna be i++ and then i’m gonna use
the comma operator and we need to decrement the value of j. so its gonna be j–. so here you guys can see inside is for loop
we are using more than one variable. so here we have separated that using the comma
operator. in this the initialisation part and also in
this updation part you guys can see that. in this condition part if you want to use
the comma operator and if you want to form a complex condition then you have to use a
logical operators. but in this case does not necessary because
we want to run this loop until we loop through all the elements of this input array and that’s
why this one condition using this variable I is enough. And now inside is for loop what we are gonna
do is we are gonna store the elements in this reverse array. so its gonna be reverse of j equal to input
of i. so now after this for loop, this reverse array
is gonna contain all the elements of this input array in reverse order. The last in that we are gonna do is, we gonna
return this reverse array. so after this for loop, before the end of
this reverse array method, we are gonna return the array and to return a value we need to use
the return keyword and here we are gonna specify reverse. that’s it. now our reverse array method is gonna take
an integer array as a parameter and its gonna reverse that passed away and its gonna return
a new array with reversed elements. so now what we are gonna do is we are gonna
call this reverse array method in our main method and we are gonna pass an array to that
and here now our reverse array method is gonna return an integer array. so to store that what we are gonna do in this
main method is we are gonna create an integer array. so its gonna be int and then it’s going to
be an array. so I just gonna declare an array and i’m gonna
call it as revmarks. and here make a note that we are not allocating the memory for
This revmark. The array returned by this riverseArray method
will be stored in this revmarks variable. so here what we are gonna do is we are gonna
write revmarks equal to then we are gonna call this riverse array method. so I just gonna copy this and paste it here.
and now to this reverse array method, we need to pass an array. so i’m gonna pass this marks array and after
that what we are gonna do is, we are gonna use a printline statement just to make our
output pretty. you know to differentiate between this marks
array and this reverse array element. So i just gonna use system.out.printline method
and i’m gonna say reversed array elements and then we are gonna call this display method
again. so its gonna be display and now we are gonna
pass This revmark array. so I just gonna copy this and paste it here and
then I’m gonna save this and I’m gonna run this program. Now you guys can see, this is the array, Marks
array which we have printed out using the display method and then here is the reversed
away from our reverse array method. so you guys can clearly see here, array elements
are been reversed. so 77 88 99 33 66 and 22. here and in this main method what we have
done is we have declared this revmarks to store the return value from this reverse array
method. what we can do is we can directly call this
display method and we can pass the return value, you know the returned array to this
display method directly. so what I’m gonna do is i’m gonna comment
in this code and this one also and we are gonna comment in this one too. so that when you get the source code of this
tutorial you guys can try it out. And here I’m gonna call the display Method
again and here what we are gonna do is we are gonna pass the return value from this
reverse array method, directly to this display method. so I’m gonna copy this and i’m gonna paste
it here and if I save this and run this program, its gonna work just like the way it was working
before. so i’m gonna run this. you guys can see there is no difference in
the previous Run. so this is how you guys can pass an array,
a single dimensional array to a method and also you guys can return a single dimensional
array from a method. so thank you for watching and Don’t forget
to subscribe to my channel. you guys can like my Facebook page @ facebook.com/learningLad
and also you guys can follow me on Twitter @ learningladEdu and also you guys can
get the source code of this tutorial in my website learninglad.com and I’ll see you next
tutorial.

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