Java FileNotFoundException even if the file exists

I'm building an app where I need to store a HashMap<Integer, User> containing users' information into a file. Whenever the program starts, if users file doesn't exist it will create a new empty file, and whenever a new user registers I call the function saveUsers() which saves the HashMap into the file. When a user wants to login, I call the function loadUsers() which reads the file and store the object in the HashMap named users. The problem is that the program always throw a FileNotFoundException whenever I call loadUsers() even if the file exists, and using the absolute path.

Here are my functions :

public void saveUsers() throws IOException {
    File file = new File(usersFile);
    FileOutputStream f = new FileOutputStream(file);
    ObjectOutputStream s = new ObjectOutputStream(f);
    s.writeObject(users);
    s.close();
}

public void loadUsers() throws IOException {
    File file = new File(usersFile);
    //System.out.println(file.exists()); always returns false
    //System.out.println(file.getAbsolutePath().exists()); always returns false
    FileInputStream f = new FileInputStream(file);
    ObjectInputStream s = new ObjectInputStream(f);
    try {
        users = (HashMap<Integer, User>) s.readObject();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    s.close();
}

Inside the login function :

try {
        loadUsers();
    } catch (IOException e) {
        System.out.println(e);
        // Here I always get this :
        // java.io.FileNotFoundException: C:\Users\Me\Desktop\users.dat
        // (The filename, directory name, or volume label syntax is incorrect)
    }

The Users class is Serializable and usersFile = "C:\\Users\\Me\\Desktop\\users.dat"

I tried using file:/// at the beginning, forward slashes and backslashes but nothing seems to work.

When I run dir C:\Users\Me\Desktop\users.dat in command prompt I get this :

Directory of C:\Users\Me\Desktop\users.dat

06/04/2020  01:03               616 users.dat
       1 File(s)            616 bytes
       0 Dir(s)  54,714,023,936 bytes free

Exception and stack trace :

java.io.FileNotFoundException: C:\Users\Me\Desktop\users.dat    
(The filename, directory name, or volume label syntax is incorrect)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(FileInputStream.java:195)
    at java.io.FileInputStream.<init>(FileInputStream.java:138)
    at com.APP.loadUsers(APP.java:710)
    at com.APP.login(APP.java:722)
    at com.APP.lambda$6(APP.java:221) 

Edit :

I tried this :

public void loadUsers() throws IOException {
    try (ObjectInputStream s = new 
    ObjectInputStream(Files.newInputStream(Paths.get(usersFile)))) {
       try {
            users = (HashMap<Integer, User>) s.readObject();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

And got this error :

> at index 33: C:\Users\Me\Desktop\users.dat <

    at sun.nio.fs.WindowsPathParser.normalize(WindowsPathParser.java:182)
    at sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:153)    
    at sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:77)     
    at sun.nio.fs.WindowsPath.parse(WindowsPath.java:94)
    at sun.nio.fs.WindowsFileSystem.getPath(WindowsFileSystem.java:255)  
    at java.nio.file.Paths.get(Paths.java:84)

The error strongly suggests there is a unicode character of some sort in that string. I suggest you delete the entire line and type it back in by hand to avoid this.

Alternatively, perhaps you 'cleaned' that name for the purposes of asking the question, in which case: Is there a fancy character in your name (something not from the ASCII range?) – then that's likely the problem.

You don't and shouldn't put file:// in front of this; the right way for this style of code is: File file = new File("C:\\Users\\Foo\\Bar");

The old Java File I/O API is notorious for generating misleading error messages. Use the newer NIO.2 API, which was added in Java 7.

You should also use try-with-resources, also added in Java 7. Unless you're stuck on ancient Java 6 or earlier, there is no good excuse for not using the newer APIs.

That would make your code look like this:

public void loadUsers() throws IOException {
	try (ObjectInputStream s = new ObjectInputStream(Files.newInputStream(Paths.get(usersFile)))) {
		try {
			users = (HashMap<Integer, User>) s.readObject();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
}

Even if this still fails, it might provide a different error, like "access denied".