if it's start of the month...do this?

Question

I want my code to empty a specific text file, when it is the beginning of each month. I have this code but it doesn't seem to work, do I have something wrong with the syntax maybe?

public void monthlyCleanse(File f){

    LocalDate localDate = LocalDate.now();

    String d = DateTimeFormatter.ofPattern("dd").format(localDate);

    System.out.println(d);

    if(d.equals("01")){


        "filename.txt".replace(toString().valueOf(f), "");
    }
}

As you can see I am changing the format to only show the day of the month, then I am checking if that day equals "01" then do something...which is to empty a text file.

Then i am calling it here...

    monthlyCleanse(new File("filename.txt"));

How can i make sure that this file is emptied?

Why convert to a string? Just use `localDate.getDayOfMonth() == 1`. — Andy Turner, Sep 08 '17 at 10:14
Also: what do you think `"filename.txt".replace(toString().valueOf(f), "");` does? — Andy Turner, Sep 08 '17 at 10:15
@Nathan My point was that it doesn't make sense ... but Andy T. already point it out. — AxelH, Sep 08 '17 at 10:19
@AndyTurner I assumed that It would replace the contents of the "filename.txt" file with "". Therefore making it empty? — Maiwand, Sep 08 '17 at 10:22
@Maiwand well, yes, but you then immediately discard the empty string. So that statement is effectively a no-op. Besides that, replacing the *name* of a file with an empty string doesn't make that file empty. — Andy Turner, Sep 08 '17 at 10:23
@AndyTurner so what would you say I should put within the if condition? So if the date does == 1. what should I use? — Maiwand, Sep 08 '17 at 10:25
@Maiwand You are not replacing the **contents** of the file with `""`. you're replacing a `String`. You should refer to this question that explains how to write in a file: https://stackoverflow.com/questions/2885173/how-do-i-create-a-file-and-write-to-it-in-java — Turtle, Sep 08 '17 at 10:29
This is a very confused question. The title is about doing something monthly. But you've solved that part (albeit in a weird way). Your actual question is about emptying a file, which would have the same answer regardless of when you do it. — slim, Sep 08 '17 at 10:30

Turtle · Answer 1 · 2017-09-08T10:31:21.373

When you do this "filename.txt".replace(toString().valueOf(f), "");, it returns a modified copy of the contents of the String "filename.txt", not the file. You should refer to this question that explains how to delete the contents of a file.

This could look like this:

if(d.equals("01")){
    PrintWriter writer = new PrintWriter(f);
    writer.print("");
    writer.close();
}

On a side note: When you call: toString().valueOf(f), it is quite confusing. You should replace it by String.valueOf(f), as it is a static function. If you look at its implementation, it returns the path of the File passed in parameter, so it has no connection with an already existing String object.

if it's start of the month...do this?

1 Answers1