@Override
  public int hashCode() {
    int result = value != null ? value.hashCode() : 0;
    result = 31 * result + (int) (timestamp ^ (timestamp >>> 32));
    return result;
  }
An immutable pair of a value, and its corresponding timestamp.

@param <V> the type of the value
samza-api/src/main/java/org/apache/samza/util/TimestampedValue.java