On Sat, 29 Mar 2008 12:43:10 -0700 (PDT), Chase Preuninger
<chasepreuninger@gmail.com> wrote, quoted or indirectly quoted someone
who said :

Think that is a feature of ZIP, not GZIP.

It is a bit complicated, because they have protected the API
for that.

But see at the code below for how to workaround it. It should
also be noted that the default level seems to be 6 and that
it will be fine for most usage.

Arne

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import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;

public class GZipFun {
    public static void gzip(String infnm, String outfnm) throws
IOException {
        FileInputStream is = new FileInputStream(infnm);
        GZIPOutputStream os = new GZIPOutputStream(new
FileOutputStream(outfnm));
        byte[] b = new byte[100000];
        int n;
        while((n = is.read(b)) > 0) {
            os.write(b, 0, n);
        }
        os.close();
        is.close();
    }
    public static void xgzip(String infnm, String outfnm, int level)
throws IOException {
        FileInputStream is = new FileInputStream(infnm);
        XGZIPOutputStream os = new XGZIPOutputStream(new
FileOutputStream(outfnm));
        os.setLevel(level);
        byte[] b = new byte[100000];
        int n;
        while((n = is.read(b)) > 0) {
            os.write(b, 0, n);
        }
        os.close();
        is.close();
    }
    public static void main(String[] args) throws Exception {
        gzip("C:\\z.txt", "C:\\z.txt.gz");
        for(int i = 0; i < 10; i++) {
            xgzip("C:\\z.txt", "C:\\z.txt.gz" + i, i);
        }
    }
}

class XGZIPOutputStream extends GZIPOutputStream {
    public XGZIPOutputStream(OutputStream out) throws IOException {
        super(out);
    }
    public void setLevel(int level) {
        def.setLevel(level);
    }
}