Java Programming Tutorial - 81 - Reading from Files Video Lecture - Java

what is going on guys welcome to your
81st Jeff torial and we are finally
going to learn how to read stuff from a
file so as you can already see I created
this Chinese dot txt file and I added
three more records to it so the first
one is Bucky the second one is the ID
number and then a name ID number name ID
number name so it has four records and a
record is pretty much um a row of data
so now let's go ahead and figure out all
right we learned how to open the file we
learned how to write this stuff on this
file but we don't know how to access it
from a Java program so that's what I'm
going to be teaching you today and the
thing I didn't tell you is before we use
scanner that scanner object to read from
our keyboard using system in but we can
actually use scanner to read from a file
as well so let's go ahead and first make
a private scanner variable so I'm going
to name mine scan or X the cursor out of
the way and now let's go ahead and just
make a method to open the file first
so public void open file and let's go
ahead and put try to open the file so
we're going to set X and again here's
where we're going to put a new scanner
and instead of putting a system in here
which would be the keyboard just put new
file and put that Chinese dot text I
spell it right yep and now instead of
reading from your keyboard it's actually
going to read from this Chinese text
file right here so that's a neat little
trick that you can do and if we get any
errors let's just go ahead and catch
those errors exceptions e
and now what do we want to do let's go
ahead and write
system.out.print line and let's go ahead
and print something like
good nods fine file looks good enough so
now we have a method to open the file
easy enough
so what method do we need after this
well
this tutorial is all about reading files
so let's go ahead and make a method to
read the data from that file so public
void just name it like read a file or
something like that
and what we want to do whooping cough
the first thing we want to do is create
a while loop and go something like this
while I'll put your file name which is X
and then we one-putt has next and what
this is going to do it's a built in
method it's going to make a while loop
and it's going to keep going until it
reaches the end of the file so it's
going to loop through this and has next
pretty much means if you hover over it
on another input so as long as there's
something there it's going to continue
as soon as there's nothing there and it
reaches the end of file this is going to
be false and this while loop is going to
break out so that's why we can work
right while X has next it pretty much
means while the file X has something in
it so what we want to do is you see each
of these records has an ID number a
first name and a last name so we're
going to want three variables to hold
those string a and let's go ahead and
copy that actually we're going to put
string a equals X dot next and what this
means is pretty much it's going to do
this well let me finish writing all my
variables that will tell you guys what
does string a equals next and this is
going to be B and C what it's going to
do is this it's going to loop through
the very first thing it sees and it's
going to assign 20 equal to a then it's
going to assign Buckey equal to B and
Roberts equal to C and then we're we're
going to put after this is we're just
going to go ahead and print those out so
system.out.print actually printf will be
better so let's go ahead and print
just three string variables so percent s
space percent s space percent s in those
variables of course are a B and C so now
what it's going to do is after it gets
those three it's going to print it out
in might want to put a new line there
and then it's going to go all right next
60 a Joe is B in Delta C now I'm going
to print all those out and it's going to
keep printing those out until it gets to
the end of the file which is right here
and then it's going to break out that
while loop so that's actually the only
thing we need in this read file method
right there so now we just need that one
last method and what this is going to do
is close the file so public void close
file just like that
and all we want this to do is close that
file X and now looks like we got
everything check for errors and now we
can go ahead and start putting it in our
main so let's go ahead and put read file
I didn't intrude probably yep R equals
new read file don't take any parameters
and now let's go ahead and put our open
file r dot read file and r dot close
file right there so now what this is
going to do is call open file to open it
read the stuff from it and close it when
we're done with it so now let's go ahead
and run this and we'll see what we got
we got pretty much exactly what is in
our text file xx Bucky Roberts it just
printed all this out it stored this in a
B C printed it out then it got three new
variables store this in a b c print out
ABC ABC and then it got to the end of
the file and a broke out so again let me
make sure that's in there and i'll tell
you guys how this worked one last time
we made a new scanner variable x because
remember we can use scanner to not only
read from our keyboard
also read from files we then made a
method to open the file right here in
which how we did that is we pretty much
set this scanner and said we're reading
from this file
Chinese dot txt which is right here and
we pretty much set the file equal to X
this error is a handling because we
programmed it awesomely and we don't
need air handling because we don't have
any errors and now we made a method to
read the file or pretty much read the
data in the file and how we did this is
we pretty much set variables equal to
each one of these items or words or
strings choose your word and then when
we got three we printed it out on the
line and then we got a new line got
three more printed it out three more
print it out and it does that until it
reaches the end of the file using the
hasnext function and last but not least
we close the file because you know it's
just good programming so that is that
for how to read a file in Java um that's
it I mean nothing else to say except
thank you guys for watching don't forget
to subscribe and I will see you next
time