public static StreamSpec getStreamSpec(String streamId, StreamConfig streamConfig) {
    String physicalName = streamConfig.getPhysicalName(streamId);
    String system = streamConfig.getSystem(streamId);
    Map<String, String> streamProperties = streamConfig.getStreamProperties(streamId);
    return new StreamSpec(streamId, physicalName, system, streamProperties);
  }
Returns the period separated system stream name for the provided {@code systemStream}. For
example, SystemStream("kafka", "topic") would return "kafka.topic".

@param systemStream the {@link SystemStream} to get the name for
@return the system stream name
samza-core/src/main/java/org/apache/samza/util/StreamUtil.java