How can I find out if a File is a file or directory if it does not exist?

Question

File.isFile() and File.isDirectory() both return false not only when the File is not the specified type, but also when the File itself does not exist on the filesystem. How can I determine whether the File represents a file or a directory when it does not exist?

Answer 1

Test File.exists() first.

Pseudo-Code (because I don't do Java :) ):

If File.Exists()
{
    If File.isFile()
    {
        bIsFile = true;
    }elseif File.isFolder()
    {
        bIsFolder = true;
    }else
    {
        //Handle error condition here
    }
}else
{
    //It does not exist. Handle that here if you care to
}

Answer 2

In general, a specific path can represent both a directory and a file. Until there is either a directory or a file created at that path, the notion of it being for one or the other is invalid.

There is however a special case. If the path ends with a path separator ('/' on Unix-like systems, '\' on Windows and maybe something completely different on other systems), then at least on Unix-like systems the path cannot be that of a file. I do not know if this is valid for all systems though.

Answer 3

You can't

The file must exists first in order to know what it IS ( I understand that if the file does not exist it IS nothing yet )

The javadoc says in both cases:

true if and only if the file denoted by this abstract pathname exists and [...]

A file that does not exists yet may be both potentially.

Answer 4

I think the answer is that you can't. Part of the reason is that it just doesn't exist. The rest of the reason has to do with the system-independence of Java. Depending on what operating system you're running on, there isn't really a difference between a file and a directory. In UNIX for example, everything is a file. Pipes, directories, links -- they're all technically files.

As it stands, the abstract pathname referenced by the File object could be either one -- until you perform either mkdir() or createNewFile() on it.

Answer 5

Your question is like asking this:

"How can I tell if this box contains a cat or a dog when it is empty?"

On the face of it, this question is nonsensical, and so is yours. If a File is a path refers to a non-existent file system object (i.e. to "nothing") then asking whether that "nothing" >>is<< a file or a directory is meaningless. It is obviously neither.

Specifically, at any instant in time all of the following predicates hold:

 file.exists() == false IMPLIES 
      file.isDirectory() == false AND file.isFile() == false

 file.isDirectory() == true OR file.isFile() == true IMPLIES 
      file.exists() == true

 file.isDirectory() == true IMPLIES 
      file.isFile() == false

 file.isFile() == true IMPLIES 
      file.isDirectory() == false