How to count the number of files in a directory, with the same file extension, in Java?

Question

I want to be able to count all the save games a user has created.

Using Java, how can I count all the files in a directory with a specific extension?

This code counts all the files regardless of extension:

public class MCVE {

    public static void main(String[] args) {
        countFiles();
    }

    private static void countFiles() {
        long amountOfFiles = 0;
        try {
            Stream<Path> files = Files.list(Paths.get("./saves"));
            amountOfFiles = files.count();
            System.out.println(amountOfFiles);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

@MadProgrammer I'm not a very experienced programmer, and I don't know anything about that. — LuminousNutria, Dec 21 '18 at 04:01
[How do I iterate over a stream in Java using for?](https://stackoverflow.com/questions/31044041/how-do-i-iterate-over-a-stream-in-java-using-for) — MadProgrammer, Dec 21 '18 at 04:02

Khalid Shah · Accepted Answer · 2018-12-21T04:34:57.680

1

Pass your extension in this function.

amountOfFiles = files.map(Path::toFile).filter(e->e.getName().endsWith(".xml")).count();

edited Dec 21 '18 at 04:34

answered Dec 21 '18 at 04:02

Khalid Shah

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Thank you, but I cannot get this to work. It always returns zero. I have tried with the ".sav" files I am trying to use, and a ".ttf" file I threw in there just to test with. – LuminousNutria Dec 21 '18 at 04:26
That it does! Thanks! – LuminousNutria Dec 21 '18 at 04:36

score 0 · Answer 2 · answered Dec 21 '18 at 04:35

I have managed to figure it out on my own. Since I couldn't figure out how to use the Path endsWith() method, I had to convert each Path object to a String, and then use the String version of the endsWith() method instead.

private static void countFiles() {
    long amountOfFiles = 0;
    try {
        Stream<Path> files = Files.list(Paths.get("./saves"));
        Iterable<Path> iterable = files::iterator;

        String fileName = "";
        for (Path p: iterable) {
            fileName = p.getFileName().toString();
            if(fileName.endsWith(".sav"))
                amountOfFiles++;
        }

        System.out.println(amountOfFiles);

        files.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

score 0 · Answer 3 · answered Dec 21 '18 at 05:26

You can use FilenameFilter and FileFilter to filter you needed file or dirctory.

File file = new File("pathname");
// fileter file name start wit Chap
file.listFiles(pathname -> pathname.getName().startsWith("Chap"));
// fileter car read file
file.listFiles(pathname -> pathname.canRead());

You can refer to the official documentation Java IO

How to count the number of files in a directory, with the same file extension, in Java?

3 Answers3