How do I use File.exists()?

[Danger_Duck]

Almost a silly question, but I want to make sure I have it right:

Java.io.File:

Say I want to know if C:\folder\file.txt exists.

Do I just do this:

File file = new File(C:\folder\file.txt);

if (file.exists()) {
//confirm existence
System.out.print("it's there dude \n");
}

Does the above work for confirming whether or not the file is there?
If so, I guess the File class doesn't ACTUALLY create new files?
Because without reading any documentation I would think the first line
actually made a file there and therefore (of course!) it will
exist...NOT

I ask because the javadoc isn't too clear-does the file instance
actually mean a new file?
Thanks to whoever can enlighten me on what this is actually doing.

File

public File(String pathname)

Creates a new File instance by converting the given pathname
string into an abstract pathname. If the given string is the empty
string, then the result is the empty abstract pathname.

Parameters:
pathname - A pathname string
Throws:
NullPointerException - If the pathname argument is null

 

[Dave Miller]

Almost a silly question, but I want to make sure I have it right:

Java.io.File:

Say I want to know if C:\folder\file.txt exists.

Do I just do this:

File file = new File(C:\folder\file.txt);

if (file.exists()) {
//confirm existence
System.out.print("it's there dude \n");
}
Yes

Does the above work for confirming whether or not the file is there?
If so, I guess the File class doesn't ACTUALLY create new files?
Because without reading any documentation I would think the first line
actually made a file there and therefore (of course!) it will
exist...NOT

File creates a file instance use FileOutputStream to write it to disk.

<snip>

 

[Tom Anderson]

Almost a silly question, but I want to make sure I have it right:

Java.io.File:

Say I want to know if C:\folder\file.txt exists.

Do I just do this:

File file = new File(C:\folder\file.txt);

if (file.exists()) {
//confirm existence
System.out.print("it's there dude \n");
}

Does the above work for confirming whether or not the file is there?
If so, I guess the File class doesn't ACTUALLY create new files?

The thing to understand is that File isn't actually a file. It's a
filename. The class is badly named, sadly. Once you've realised that, i
think everything else is clear.

Because without reading any documentation I would think the first line
actually made a file there and therefore (of course!) it will
exist...NOT

That's definitely the logical thing to think - and sadly, it isn't true!
But once you think of it as creating a filename rather than an actual
file, it makes sense.

tom

 

[Roedy Green]

File file = new File(C:\folder\file.txt);

File file = new File( "C:/folder/file.txt");
or
File file = new File( "C:\\folder\\file.txt");

see http://mindprod.com/jgloss/file.html

 

[Danger_Duck]

The thing to understand is that File isn't actually a file. It's a
filename. The class is badly named, sadly. Once you've realised that, i
think everything else is clear.


That's definitely the logical thing to think - and sadly, it isn't true!
But once you think of it as creating a filename rather than an actual
file, it makes sense.

tom

Thanks-that clarifies things. File=filepath

And Roedy-yes, you're right, that's what I meant to put
I have the string stored separately in my program anyway so I guess I
wasn't paying that much attention when I was asking the question.

 

[Roedy Green]

Thanks-that clarifies things. File=filepath

The File class is primarily for composing and taking apart filenames.
It has a few other methods like delete and exists that actually do
something to files. But it most definitely does not create or open a
file.

 

[magloca]

Harold Shand @ Thursday 28 August 2008 21:44:

Roedy Green wrote: [snip]

The File class is primarily for composing and taking apart filenames.
It has a few other methods like delete and exists that actually do
something to files. But it most definitely does not create or open a
file.

Hmm. File.createNewFile() must be quite an embarrassing misnomer,
then.

But it most definitely does not *implicitly* create or open a file.

m.

 

[EJP]

But it most definitely does not *implicitly* create or open a file.

Bzzt. Of course it does. RTFM. Or try it and see.

'Atomically creates a new, empty file named by this abstract pathname if
and only if a file with this name does not yet exist.'

 

[Roedy Green]

Hmm. File.createNewFile() must be quite an embarrassing misnomer, then.

To be more precise, new File does not create a file.

 

[magloca]

EJP @ Sunday 31 August 2008 11:30:

Bzzt. Of course it does. RTFM. Or try it and see.

'Atomically creates a new, empty file named by this abstract pathname
if and only if a file with this name does not yet exist.'

Maybe I snipped too much of the preceding discussion leading up to my
comment. The "it" in my statement refers to the File class, not the
createNewFile() method. Instantiating a File object doesn't implicitly
create the file in the filesystem; invoking the createNewFile() does,
explicitly.

Sorry about that.

m.

 

[Mike Schilling]

Bzzt. Of course it does. RTFM. Or try it and see.

'Atomically creates a new, empty file named by this abstract
pathname
if and only if a file with this name does not yet exist.'

Looks pretty explict to me.

 

[Daniele Futtorovic]

Looks pretty explicit to me.

I think that was his point. It's not implicit.