TrueZip - How to get Size of a Folder within an Zip Archive

Question

is there a way to get the Size of a folder with TrueZip without doing it myself recursively? I'm concerned about the runtime since I'm dealing with Archives that contain lots of files.

Using TrueZip 7.7.9

Answer 1

OK, here is a simple test using only the standard Java 7 API; it uses the bundled JSR 203 implementation for zips:

public final class Test
{
    public static void main(final String... args)
        throws IOException
    {
        final Path zip = Paths.get("/home/fge/t.zip");

        final URI uri = URI.create("jar:" + zip.toUri());

        try (
            final FileSystem fs = FileSystems.newFileSystem(uri, Collections.emptyMap());
            final DirectoryStream<Path> stream = Files.newDirectoryStream(fs.getPath("/"));
        ) {
            for (final Path entry: stream)
                System.out.println(Files.size(entry));
        }
    }
}

The zip above only contains files at the top level, not directories.

This means that you can use this API to correctly compute the size of files in a zip; without the need to uncompress.

You use Java 7; therefore, what you want to do is probably to use a FileVisitor which computes the size of all regular files for you.

Here I have made a crude hack which uses Files.size(); note that in a FileVisitor, when you visit a filesystem entry which is not a directory, you have an instance of BasicFileAttributes coming along from which you can retrieve the size().

Javadoc here; and use Files.walkFileTree().

With Java 8, this is much simpler, you could use Files.find() instead.