Get size of folder or file

Question

How can I retrieve size of folder or file in Java?

Answer 1

in linux if you want to sort directories then du -hs * | sort -h

Answer 2

• Works for Android and Java
• Works for both folders and files
• Checks for null pointer everywhere where needed
• Ignores symbolic link aka shortcuts
• Production ready!

Source code:

   public long fileSize(File root) {
        if(root == null){
            return 0;
        }
        if(root.isFile()){
            return root.length();
        }
        try {
            if(isSymlink(root)){
                return 0;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return 0;
        }

        long length = 0;
        File[] files = root.listFiles();
        if(files == null){
            return 0;
        }
        for (File file : files) {
            length += fileSize(file);
        }

        return length;
    }

    private static boolean isSymlink(File file) throws IOException {
        File canon;
        if (file.getParent() == null) {
            canon = file;
        } else {
            File canonDir = file.getParentFile().getCanonicalFile();
            canon = new File(canonDir, file.getName());
        }
        return !canon.getCanonicalFile().equals(canon.getAbsoluteFile());
    }

Answer 3

Here's the best way to get a general File's size (works for directory and non-directory):

public static long getSize(File file) {
    long size;
    if (file.isDirectory()) {
        size = 0;
        for (File child : file.listFiles()) {
            size += getSize(child);
        }
    } else {
        size = file.length();
    }
    return size;
}

Edit: Note that this is probably going to be a time-consuming operation. Don't run it on the UI thread.

Also, here (taken from https://stackoverflow.com/a/5599842/1696171) is a nice way to get a user-readable String from the long returned:

public static String getReadableSize(long size) {
    if(size <= 0) return "0";
    final String[] units = new String[] { "B", "KB", "MB", "GB", "TB" };
    int digitGroups = (int) (Math.log10(size)/Math.log10(1024));
    return new DecimalFormat("#,##0.#").format(size/Math.pow(1024, digitGroups))
            + " " + units[digitGroups];
}

Answer 4

For Java 8 this is one right way to do it:

Files.walk(new File("D:/temp").toPath())
                .map(f -> f.toFile())
                .filter(f -> f.isFile())
                .mapToLong(f -> f.length()).sum()

It is important to filter out all directories, because the length method isn't guaranteed to be 0 for directories.

At least this code delivers the same size information like Windows Explorer itself does.

Answer 5

The File object has a length method:

f = new File("your/file/name");
f.length();

Answer 6

java.io.File file = new java.io.File("myfile.txt");
file.length();

This returns the length of the file in bytes or 0 if the file does not exist. There is no built-in way to get the size of a folder, you are going to have to walk the directory tree recursively (using the listFiles() method of a file object that represents a directory) and accumulate the directory size for yourself:

public static long folderSize(File directory) {
    long length = 0;
    for (File file : directory.listFiles()) {
        if (file.isFile())
            length += file.length();
        else
            length += folderSize(file);
    }
    return length;
}

WARNING: This method is not sufficiently robust for production use. directory.listFiles() may return null and cause a NullPointerException. Also, it doesn't consider symlinks and possibly has other failure modes. Use this method.