Question

In Java I want to create a file from and save the data on it. The File name with path is taken from user. Now if user give invalid path like C:\temp\./user\fir/st.csv which is an invalid path because "." and / are in the path and on windows operating system "\" is used as path separator.

Before executing the program(a command line tool), there was no temp folder in C:\ directory, but when I run the program it creates temp folder then in temp it creates user then in user it create fir folder and finally st.csv in it. While I want that if such type of invalid path or file name is given by the user user should be noticed by message "Invalid path or file name".

What should I do? Program code is like below:

public class FileTest {
    public static void main(String args[]) {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Please enter path:");
            String path = br.readLine();
            File file = new File(path);
            String path1 = file.getParent();
            File file2 = new File(path1);
            if (!file2.exists()) {
                System.out.println("Directory does not exist , So creating directory");
                file2.mkdirs();
            }
            if (!file2.exists()) {
                System.out.println("Directory can not be created");
            } else {
                FileWriter writer = new FileWriter(file);
                PrintWriter out = new PrintWriter(writer);
                System.out.println("Please enter text to write on the file, print exit at new line to if finished");
                String line = "";
                while ((line = br.readLine()) != null) {
                    if (line.equalsIgnoreCase("exit")) {
                        System.out.println("Thanks for using our system");
                        System.exit(0);
                    } else {
                        out.println(line);
                        out.flush();
                    }
                }
            }
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Now if I give the path as C:\tump\./user\fir/st.csv then it create tump folder in C drive , then user in tump, then fir in user folder then st.csv file in it.

Answer 1

In my case which I required this works

if(!path.equals(file.getCanonicalPath())){
                System.out.println("FAILED:Either invalid filename, directory or volume label , syntax error");
                System.exit(0);
            }

By adding this code just after
File file=new File(path);
it will work fine and will notice the user if given path is incorrect

As there is only two options either java will create the file on some path which will be canonical path or if not able to create the file it will give exception. So if there is any mismatch in the path given by the user and canonical path then it means user type wrong path which java can not create on the file system, so we will notice the user, or if java give exception then we can catch it and will notice the user for incorrect path