相对文件路径在Java中不起作用

Question

After reading that is it possible to create a relative filepath name using "../" I tried it out.

I have a relative path for a file set like this:

String dir = ".." + File.separator + "web" + File.separator + "main";

But when I try setting the file with the code below, I get a FileNotFoundException .

File nFile= new File(dir + File.separator + "new.txt");

Why is this?

Answer 1

nFile prints: "C:\\dev\\app\\build\\..\\web\\main"

and

("") file prints "C:\\dev\\app\\build"

According to your outputs, after you enter build you go up 1 time with .. back to app and expect web to be there (in the same level as build ). Make sure that the directory C:\\dev\\app\\web\\main exists.

You could use exists() to check whether the directory dir exist, if not create it using mkdirs()

Sample code:

File parent = new File(dir);
if(! parent.exists()) {
    parents.mkdirs();
}
File nFile = new File(parent, "new.txt");

Note that it is possible that the file denoted by parent may already exist but is not a directory, in witch case it would not be possible to use it as parent. The above code does not handle this case.

Answer 2

Why wont you take the Env-Varable "user.dir"?

It returns you the path, in which the application was started from.

System.getProperty(user.dir)+File.separator+"main"+File.separator+[and so on]