Extract files from *.gz extension

I have successfully extracted *.gz from *.tgz and now I have no idea how to actually extract final files from *.tgz.

There are some options using custom packages but that's not an option for me, I need to use standard Java packages only.

What I tried is using same function that I use for *.tgz for *.gz but it doesn't work.

java.util.zip.ZipException: Not in GZIP format 1.gz

Here is function that is extracting *.tgz files.

public String ExtractFile(String path) {
    try {
        File newFile = new File(this.getFullPathWithoutExtension(path) + ".gz");

        GZIPInputStream gStream;
        FileOutputStream outStream;
        try (FileInputStream fileStream = new FileInputStream(path)) {
            gStream = new GZIPInputStream(fileStream);
            outStream = new FileOutputStream(newFile);
            byte[] buf = new byte[1024];
            int len;
            while ((len = gStream.read(buf)) > 0) {
                outStream.write(buf, 0, len);
            }
        }
        gStream.close();
        outStream.close();

        newFile.createNewFile();

        return newFile.getPath();

    } catch (Exception e) {
        System.out.print(e);
    }

    return null;
}

TL;DR; *.tgz files extracted to *.gz files, however *.gz files cannot be extracted.