This method will get a InputStream as input and return a String of response

readFromStream.java

/**
     * Convert the {@link InputStream} into a String which contains the
     * whole JSON response from the server.
     */
    private static String readFromStream(InputStream inputStream) throws IOException {

        StringBuilder output = new StringBuilder();
        if (inputStream != null){
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
            BufferedReader reader = new BufferedReader(inputStreamReader);
            String line = reader.readLine();
            while (line != null){
                output.append(line);
                line = reader.readLine();
            }
        }

        return output.toString();
    }