What is the fastest way to extract 1 file from a zip file which contain a lot of file?

Question

I tried the java.util.zip package, it is too slow.

Then I found LZMA SDK and 7z jbinding but they are also lacking something.

The LZMA SDK does not provide a kind of documentation/tutorial of how-to-use, it is very frustrating. No javadoc.

While the 7z jbinding does not provide a simple way to extract only 1 file, however, it only provide way to extract all the content of the zip file. Moreover, it does not provide a way to specify a location to place the unzipped file.

Any idea please?

Answer 1

What does your code with java.util.zip look like and how big of a zip file are you dealing with?

I'm able to extract a 4MB entry out of a 200MB zip file with 1,800 entries in roughly a second with this:

OutputStream out = new FileOutputStream("your.file");
FileInputStream fin = new FileInputStream("your.zip");
BufferedInputStream bin = new BufferedInputStream(fin);
ZipInputStream zin = new ZipInputStream(bin);
ZipEntry ze = null;
while ((ze = zin.getNextEntry()) != null) {
    if (ze.getName().equals("your.file")) {
        byte[] buffer = new byte[8192];
        int len;
        while ((len = zin.read(buffer)) != -1) {
            out.write(buffer, 0, len);
        }
        out.close();
        break;
    }
}