import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.zip.GZIPInputStream;
public class Main {
public static void main(String[] args) throws Exception {
int sChunk = 8192;
String zipname = "a.txt.gz";
String source = "a.txt";
FileInputStream in = new FileInputStream(zipname);
GZIPInputStream zipin = new GZIPInputStream(in);
byte[] buffer = new byte[sChunk];
FileOutputStream out = new FileOutputStream(source);
int length;
while ((length = zipin.read(buffer, 0, sChunk)) != -1)
out.write(buffer, 0, length);
out.close();
zipin.close();
}
}