public static void lookupSomethingInZip(InputStream is) throws IOException {
        ZipInputStream zipInputStream = new ZipInputStream(is);
        String entryName = "";
        ZipEntry entry = zipInputStream.getNextEntry();

        while (entry!=null) {
            entryName = entry.getName();
            if (entryName.endsWith("zip")) {
                //recur if the entry is a zip file
                lookupSomethingInZip(zipInputStream);
            }

            if (entryName.endsWith("txt")) {
                String str =
                        new BufferedReader(new InputStreamReader(zipInputStream))
                                .lines().collect(Collectors.joining("\n"));
                System.out.println(str);
                // if we need only first file
                break;
            }
            //do other operation with the entries..

            entry = zipInputStream.getNextEntry();
        }
    }