To decode bytes from an InputStream, you can use an InputStreamReader. Then, a BufferedReader will allow you to read your stream line by line.
Your code will look like:
ByteArrayInputStream bais = new ByteArrayInputStream(responseBytes);
GZIPInputStream gzis = new GZIPInputStream(bais);
InputStreamReader reader = new InputStreamReader(gzis);
BufferedReader in = new BufferedReader(reader);
String readed;
while ((readed = in.readLine()) != null) {
System.out.println(readed);
}