Java Programming Tutorial - 78 - File Class Video Lecture - Java Programming

what is going on everybody is Bucky and
I am kind of sick right now so if I
sound a little stuffy or I blow my nose
there in this tutorial then I guess you
guys are just going to have to deal with
it but I'm going to teach you some Java
in the mean time so let's go ahead and
get started
actually we took a break from gooeys for
the next couple toriel's I'm going to be
teaching you something about files now
you can create and modify files in Java
just like most other programming
languages if you guys are saying all
right what exactly is a file useful for
I'll give you guys the quick 1/2 of the
main thing it's useful for so far we
created computer programs that use like
variables and stuff like that like store
the number 5 and X or store like the
name Bucky and um Y or something like
that but once they end their program
then all of these variables and methods
are all gone so if we want to like keep
it in a database then we actually need
to like keep it in a text file so that
way when they run the program again then
all their information is there and they
don't you know it's not just like a
program that you can run once and it
forgets about it that way it can store
your information on the computer then
when you run your program again we can
automatically load the values and stuff
and get them again
so what we going over we're actually
building a program later on but for now
let me get typing some code before I
lose you guys so let's go ahead and
import the file class so Java dot IO dot
file or you can import everything well
that's good enough and what the file
class does is this is real simple it
doesn't create files or anything all
this class does is give you info about
files like whether it exists um has a
couple things like length the path the
parent stuff like that right now what
we're going to be doing is testing
whether a file exists on our computer
and this is useful for things like if
you're creating a program to make a file
for the first time if it already exists
you don't want to create one again
or else is going to delete it so you
want to see if it's there first and then
if it's there you can migrate to it if
it's not there then you can create it so
simple enough
what you do is type the file class we'll
name X you can name it whatever you want
and then type new file and what this
does is the constructor takes the path
of the file so I actually know that I
have a file in C and you actually have
to do this capitalize your director
whatever it is and if you do well I'll
show you guys test is in the directory
and I have a file named Greg dot txt
right there so normally this would work
and that's a valid of path name but the
thing is you know when we're working
with strings that that little backslash
is the escape character so this is
whenever you put this this is going to
try to escape this T and put a tab in G
and stuff like this so what we need to
do when we're working with path names
and windows is actually need to put two
backslashes like this and when we do
this it views this is only one backslash
because remember whenever we do
backslash with a string then it's going
to try to escape it because that's just
how windows is so actually whenever you
do path names do two backslashes if
you're working with windows if you're
working with Linux I think is a front
slash bar I'm not sure so now now that
we have this file that is stored in the
variable X we can do a couple things
with what we're going to be doing this
tutorial is simply check if it exists so
along with many of the built-in methods
we can do if X well we just did BX and
we'll just shortcut it right there if X
exists and if we hover over this it says
test whether the file or directory
pretty much exit exists so if Greg dot
txt exists then what do we want to do
let's go
stuffy nose system.out.print line and we
can print something like
we can actually have X dot getname and
that'll be pretty cool and we'll just
add something like exist so it will be
like Greg dot txt exists or if it
doesn't while we'll insert a file that
doesn't exist later so I can tell you
guys what it does and system.out.print
line and we'll say this thing doesn't
exist and make sure you almost type
everything wrong so which I did so now
we can go ahead and run this program and
see what we get
it says Greg txt exists and I probably
should put a space right there but I
didn't and what is going on is this if
you look at my computer right here and
you go to see test and this is a C and
the test is right here a file named Greg
dot txt does exist but what if you had a
file name in here like um like that see
that's what I could think of off the top
of my head if you run this and click OK
it's going to say this thing doesn't
exist so that is how you can pretty much
look for files in their existence
using the file name and the exist
properties in I also taught you another
one the get name pretty much to get the
name of it and that's a quick cute
little tutorial and let's see if there's
anything else I didn't cover and that's
pretty much it for this tutorial and in
the next story I'm actually going to
show you guys alright we already test if
it existed or not if a file doesn't
exist then how do we create one I mean
of course we can go to our computer
right here and create a file like this
but we want to create one in Java
program in language so that's why I'm
going to be teaching you in the next
tutorial so for now thank you guys for
watching study this and again review one
more time you create an object from the
file class and is this constructor it
takes the path the name of the file and
remember when you're working with
strings you got to escape the back
then you test whether it exists if it
does exist run load code to do anything
and if it doesn't exist then you usually
in here you want to write code to create
the file but for now I just want to let
write a little prompt saying this thing
doesn't exist so thank you guys for
watching I hope you learned a little
something don't forget to subscribe and
now we'll see you next time